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!_!__:

Mac,

icrosoft BASIC Works

More Output from your Mic
C Cursor Control for the CT
KIM/SYM H

You can use

MICRO PLUS
as a

SINGLE BOARD COMPUTER

OEM BUILDING BLOCK

INTELLIGENT TERMINAI

m<
In

frc

MICRO PLUS is a 6502-based Single Board Computer with
extensive video capabilities, communications support and keyboard
interface. As an OEM Building Block, it allows selection of the keyboard,
ranitor, enclosure and power supply best suited to your application. As an
itelllgent Terminal, it provides full RS232 and 20 mA communication at baud rates
om 50 to 19.2K, with superior text-editing features. It may be combined with FLEXI
PLUS to form a Sophisticated System with 8" and 5V4" diskettes, an IEEE-488 controller,
numerous I/O ports, up to 56K memory, and an optional 6809 microprocessc

Video Features:

• Programmable screen format
up to 1 32 characters by 30 lines

• Reverse video on character-by-
character basis

• EPROM character sel for user-
definable characters

• RAM character set for
dynamically changing characters
under program control

• Light pen input

• Programmable character width

• Up to 4K display memory

Communications Features:

• Programmable baud rates from
50 to 19.2K baud

• Parity generation and checking

• Programmable word length and
' stop bits

• Full-duplex or half-duplex
operation

• Both RS232C and 20-milliamp
current loop interfaces provided

• ASCII keyboard interface

Call or write for free catalog.
Letjjs build your custom system.

| — I1TO3

J □n(3(£)oflp[a1J1Ja()Sll ,

Monitor Features:

• Memory examine and modify

• Auto-increment mode

• Single-step

• Break at specified address

• Break on specified op code

Editor Features:

• Cursor up, down,
home

• Scroll up/down

• Insert/delete line or character

• Fill/clear line or window

• Find character

• Set/clear window limits

System Features:

• Up to 7K RAM— 4K
RAM, 2K programmable char-
acter generator RAM (which
may be used for program RAM),
1 K program RAM

• MicroMon 2 operating system
software in EPROM

>Can be directly expanded with
DRAM PLUS, FLEXI PLUS and
PROTOPLUS

• Single voltage required + 5V

34 Chelmsford St., Chelmsford, MA 01824 fi ffi
617/256-3649

MICRO PLUS TCB-1 1 1 $375

Communications option 50

Documentation 10

For US, add $3.00 surface postage.
Prices quoted are for US only. For
foreign shipments write for rates.
Massachusetts residents add 5% sales
tax.

tttSA

mmimmmmn

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■•■■' ,■ ■:■■

Turn your Apple into the world's
most versatile personal computer.

The SoftCard™ Solution. SoftCard
turns your Apple into two computers.
A Z-80 and a 6502. By adding a Z-80
microprocessor and CP/M to your
Apple, SoftCard turns your Apple into
a CP/M based machine. That means
you can access the single largest body
of microcomputer software in exist-
ence. Two computers in one. And, the
advantages of both.

Plug and go. The SoftCard system
starts with a Z-80 based circuit card.
Just plug it into any slot (except 0) of
your Apple. No modifications required.
SoftCard supports most of your Apple
peripherals, and, in 6502 -mode, your
Apple is still your Apple.

CP/M for your Apple. You get CP/M
on disk with the SoftCard package. It's
a powerful and simple-to-use operating
system. It supports more software
than any other microcomputer operat-
ing system. And that's the key to the
versatility of the SoftCard/Apple.

CIRCLE READER SERVICE NUMBER

BASIC included. A powerful tool,
BASIC-80 is included in the SoftCard
package. Running under CP/M, ANSI
Standard BASIC-80 is the most
powerful microcomputer BASIC
available. It includes extensive disk I/O
statements, error trapping, integer
variables, 16-digit precision, exten-
sive EDIT commands and string func-
tions, high and low-res Apple graphics,
PRINT USING, CHAIN and COM-
MON, plus many additional com-
mands. And, it's a BASIC you can
compile with Microsoft's BASIC
Compiler.

More languages. With SoftCard and
CP/M, you can add Microsoft's ANSI
Standard COBOL, and FORTRAN, or

Basic Compiler and Assembly Lan-
guage Development System. All, more
powerful tools for your Apple.
Seeing is believing. See the SoftCard
in operation at your Microsoft or Apple
dealer. We think you'll agree that the
SoftCard turns your Apple into the
world's most versatile personal
computer.

Complete information? It's at your
dealer's now. Or, we'll send it to you
and include a dealer list. Write us. Call
us. Or, circle the reader service card
number below.

SoftCard is a trademark of Microsoft. Apple II and
Apple II Plus are registered trademarks of Apple
Computer. Z-80 is a registered trademark of Zilog,
Inc. CP/M is a registered trademark of Digital
Research, Inc.

Microsoft Consumer Products, 400 108th Ave. N.E.,
Bellevue, WA 98004. (206) 454-1315

80 COLUMN GRAPHICS

The image on the screen was created
by the program below.

' 10 VISMEMs CI.EAM

20 P=160: Q*100|

30 XP»144: XR»lij5*3. 1415927
' 40 ¥P«56s m*l8ffeP»64
' SO XF»XR/XP: 5fF*tp/yH: ZF»XR/ZP

60 FOB ZI«-Q TO: 6-1

70 IP. ZK-ZP ORZI>ZP GOTO 150

80 2T-ZI*XP/ZPj ez»zi
i 90 XL«nST{.5+SQR[(XP*XP-ZT*ZT))
100 POP XI«-XL TO XL
110 XT>SQR{XI*XI+ZT*ZT)*XF: XX=XI
120 YX»<SIN(XT)*lp*SIN<3*XT))*ra
130 GOSOB 170 ! !
140 NEXT XI I
150 NEXT ZX ' I
160 STOP

170 X1*XX+ZZ+P . t
180 X1»?Y-ZZ+Q

190 GMODE Is MOVE! XI, VI: WRPIX
200 IF Xl*0 GOTO* 220

GMODE 2s LIN8 X1,Y1-1,X1,0

CBIVI W The Integrated

' Visible Memory for
the PET has now been
redesigned for the new
12" screen 80 column
and forthcoming 40
column PET computers
from Commodore. Like
earlier MTU units, the
new K-1 008-43 package
mounts inside the PET
case for total protection.
f To make the power and
flexibility of the 320 by 200
bit mapped pixel graphics display easily accessible, we have
designed the Keyword Graphic Program. This adds 45
graphics commands to Commodore BASIC. If you have been
waiting for easy to use, high resolution graphics for your
PET, isn't it time you called MTU?

K-1008-43M Manual only $10 (credited toward purchase)
k-1 008-43 Complete ready to install package $495

Mastercharge and Visa accepted

Write or call today for our full line catalog describing all
MTU 6502 products, including our high speed 8" Floppy
Disk Controller for up to 4 megabytes of PET storage.

■

210

220 RETURN

I Micro Technology Unlimited

/ 28(]B Hillshorouqh Strenl
■ PO Box l?!06
RjlBiqh NC 276D:i USA

NOW 80 COLUMN PETS CAN HAVE MTU HIGH RESOLUTION GRAPHICS

NO. 36

MAY 1981

STAFF

Editor/Publisher
ROBERT M. TRIPP

Associate Publisher
RICHARD RETTIG

Associate Editor
MARY ANN CURTIS

Special Projects Editor
MARJORIE MORSE

Art Director
GARY W. FISH

Typesetting
EMMALYN H.

BENTLEY

Advertising Manager
L. CATHERINE BLAND

Circulation Manager
CAROL A. STARK

MICRO Specialists
APPLE: FORD CAVALLARI
PET: LOREN WRIGHT
OSI: PAULGEFFEN

Comptroller
DONNA M. TRIPP

Bookkeeper
KAY COLLINS

JMCRW i S published monthly by:
MICRO INK, Inc.. Chelmsford, MA 01824
Second Class postage paid at:
Chelmsford, MA 01824 and Avon, MA

02322
USPS Publication Number: 483470
ISSN: 0271-9002

Subscription Rates: Per year

U.S. $18.00

Foreign surface mail $21.00

Air mail:

Europe $36.00

Mexico, Central America $39.00

Middle East, North Africa $42.00

South America, Central Africa $51 .00

South Africa, Far East,

Australasia $60.00

For back issues, subscriptions, change

of address or other information, write to:

MICRO

P.O. Box 6502

Chelmsford, MA 01824

or call

617/256-5515

/AJCftO

THE 6502 JOURNAL

CONTENTS

Q MACAPPLE

y Shorthand for commonly used Integer BASIC commands
By David Lubar

H KIM/SYM HOME ACCOUNTING SYSTEM
1 o Simple application requiring little hardware
By Robert Baker

A ft MORE OUTPUT FROM YOUR MICRO

I y Add extra output bits to your AIM, SYM, KIM, Superboard or C1 P
By H.H. Aumann

00 APPLESOFT VARIABLE DUMP
C.O Handy debugging utility for Applesoft in ROM
By Scott D. Schram

. HOW MICROSOFT BASIC WORKS

01 Explanation of variables and FNX definitions
By Greg Paris

on SYM-1 COMMUNICATIONS INTERFACE
jy Direct messages to SYM or modem
By Nicholas J. Vrtis

. - APPLE MEMORY MAPS, PART 2
40 Listing and program description of memory maps
By Peter A. Cook

- n THE ATARI DULCIMER
Oy Simulation of a 3-string dulcimer, in real time
By Mike Dougherty

e _ AN INEXPENSIVE WORD PROCESSOR
DO Interface an IBM 2740 terminal to an 8-bit parallel port
By William F. Pytlik

_ . TINY PILOT FOLLOW-UP

f\ More information about Tiny, plus a programming example
By Nicholas J. Vrtis

_- CURSOR CONTROL FOR THE C1 P

/ O Give your C1P user-selectable windows, one-key screen clear, and the

ability to edit

By Kerry V. Lourash

. PROTECTING MEMORY FROM DOS
O \ Protect and use RAM above DOS
By Glenn R. Sogge

DEPARTMENTS

5 Editorial — The Changing Scene — R.M. Tripp

6 Letterbox

17 Challenges — Paul Geffen

25 Microprocessors in Medicine — Jerry W. Froelich, M.D.

40 Annual Index

62 PET Vet — Loren Wright

72 Microbes

88 The MICRO Software Catalog: XXXII

92 6502 Bibliography: Part XXXII — William R. Dial

95 Advertisers' Index

No. 36 -May 1981

MICRO - The 6502 Journal

DATA CAPTURE 4.0

The most advanced and easiest to use telecommunications program for use
with the M1CROMODEM II® or the Apple COMMUNICATIONS CARD®

Q. Will DATA CAPTURE 4.0 work with my Communica-
tions Card®' and a modem?

A. It makes using the Comm. Card almost as easy as using
the Micromodem 0.

Q. Do I rreed an extra editor to prepare text for transmis-
sion to another computer?

A. No. DATA CAPTURE 4.0 gives you control of the text
buffer. You can use DATA CAPTURE 4.0 to create text.

Q. Can I edit the text I have prepared?

A. Yes. You can insefl lines or delete any lines from the text.

Q. How about text I have captured. Can I edit that?

A. As easily as the text you have prepared yourself. You can
delete any lines you don't want to print or save to a disk file.
You can also insert lines into the text.

Q. Just how much text can 1 capture with DATA
CAPTURE 4.0? i

A If the system with yitiich you are communicating accepts a
stop character, moist use a Control S, you can capture an
unlimited amount qf text.

Q. How does that work? And do I have to keep an eye on
how much r have already captured?

A. When the text buffer is fuH the stop character is output to
the other system. Then DATA CAPTURE 4.0 writes what
has been captured up to that point to a disk file. This is
done automatically!

Q, Then what happens?

A. Control is returned to you and you can send the start
character to the other system. This generally requires
pressing any key, the RETURN key or a Control Q.

Q. Are upper and lower case supported if I have a Lower
Case Adapter?

A. Yes. If you don't have the adapter an upper case only
version is also provided on the diskette.

Q. Do I need to have my printer card or Micromodem \V*
or Communications Card** in any special slot?

A. No. All this is taken care of when you first run a short
program to configure DATA CAPTURE 4.0 to your system.
Then you don't have to be concerned with it again. If you
move your cards around later you can reconfigure DATA
CAPTURE 4.0.

Q. Do I have to build a file on the other system to get it
sent to my Apple?

A No. if the other system can list it you can capture it.

Q. How easy Is it to transmit text or data to another
system?

A. You can load the text or data into DATA CAPTURE 4.0
from the disk and transmit It Or you can transmit what you
have typed into DATA CAPTURE 4.0.

a How can I be sure the other system receives what I
sendit?

A. If the other system works in Full Duplex, it 'echoes' what
you send it, then DATA CAPTURE 4.0 adjusts its sending
speed to the other system and won't send the next charac-
ter until it is sure the present one has been received. We
call thai 'Dynamic Sending Speed Adjustment'.

Q. What if the other system works only In Half Duplex.

A. A different sending routine is provided for use with Half

Duplex systems.
Q. What If I want to transmit a program to the other

system?
A No problem. You make the program into a text (Re with a

program that is provided with DATA CAPTURE 4.0, load it

into DATA CAPTURE 4.0 and transmit it.

Av--:

Q. What type files can I read and save with DATA
CAPTURE 4.0?

A. Any Apple DOS sequential text file. You can create and
edit EXEC files, send or receive VISCtAlC© data files,
send or receive text files created with any editor that uses
text files.

Q. Can t leave DATA CAPTURE 4,0 running on my Apple
at home and use it from another system?

Yes. If you are using the f^cromodem \f® you can call
DATA CAPTURE 4.0 from another system. This is handy if
you are at work and want to transmit something to your
unattended Apple at home.

Where can I buy DATA CAPTURE 4.0?

Your local Apple dealer. If he doesn't have it ask him to
order it. Or if you can't wait order it directly from Southeast-
ern Software. The price is S65.00. To order the Dan
Paymar Lower Case Adapter add $64.95 and include the
serial number of your Apple.

If I order it directly how can I pay for it?

We accept Master Charge. Visa or your personal check.
You will get your order shipped within 3 working days of
when we receive it no matter how you pay for it. Send your
order to us at the address shown or call either of the
numbers in this advertisement You can call anytime of
day, evening or Saturdays.

Q. I bought DATA CAPTURE 3.0 and DATA CAPTURE 4.0
sounds so good I want this version. What do I do to
upgrade?

A. Send us your original DATA CAPTURE 3.0 diskette and
documentation, the $35.00 price difference and $2.50 for
postage and handling. We will send you DATA CAPTURE
4 .0 within 3 working days of receiving your order.

0. What kind of support can I expect after I buy it?

A. If you have bought from Southeastern Software in the past
you know we are always ready to answer any questions
about our products or how to use them.

Requires DISK II®, Applesoft lr» and 48K of Memory

DATA CAPTURE 4.0©

* Apple", Apple II Phis™. Disk ll» and APPLESOFT lt» ere trademarks o) Apple
Computer Company.

■ Micromodem ll» is a trademark of D.C. Hayes Associate*, Inc.

• Viacalc(g>-Copyngnt by Software Arts. Inc.

We welcome your personal
check. We also accept Visa and Master Charge.

Southeastern Software

Dept. MK

6414 Derbyshire Drive • NewOrlearts, LA 70126

504/246-8438 504/246-7937

QsV

MICRO -The 6502 Journal

No. 36 -May 1981

IMCftO

Editorial

The Changing Scene

With this issue, MICRO completes
its fourth volume. This fact inspired
me to spend some time reviewing
MICRO'S past, its position now, and its
future.

The Past

The microcomputer world of 1977
was very different from today. The first
wave or microcomputerists— the hard-
ware types who could build a system
from a kit or scratch— has started to
decline in numbers and in importance.
A second generation has emerged, com-
posed of individuals with computer
knowledge who are not interested in
building a microcomputer. Early pur-
chasers of the 6502 were true pioneers.
There was no certainty that the new
6502 would survive in the already
established 8080/6800 world. There
was little vendor support for the 6502,
no books, and mysteriously little
material appearing about it in national
computer magazines.

MICRO was started to provide a for-
mal, regular publication with provision
for quality 6502-based advertising. Early
MICRO articles- discussed basic prob-
lems encountered in getting systems to
operate, and presented new 6502-based
products. MICRO was aimed at the
knowledgeable user who possessed
some programming skills, but might be
a novice in the microcomputer field.

The Present

Four years have witnessed the ex-
plosion of the Apple II, the addition of
the AIM, SYM, Atari, OSI Superboard
and Challenger systems, and the
growth of the PET/CBM systems. Now
thousands of programs are available.
The 6502 has moved from a poor third,
behind the 8080 and 6800 in the per-
sonal computing market, to a strong
position ahead of both of these pro-
cessors and equal to the Z80. Support
for the 6502 is much broader now.
There are many magazines devoted to
the 6502 or one of its microcomputers;
major microcomputer national maga-
zines now offer 6502-related material
on a regular basis; book shelves are well
stocked with 6502 books.

The needs of today's 6502 users are
changing. They are not buying a micro
to get into microcomputers— they are
buying micros to solve problems. To-
day's users are buying larger systems,
and may require 80-character upper and
lower case displays, quality keyboards,
sophisticated disk systems, printers
and more. They need ready-to-use soft-
ware, and are willing to pay for it.

To serve this expanded 6502
population, MICRO has made many
changes over the years, including the
addition of news and idea columns.
MICRO now includes articles which
are less technical in nature, plus
generalized material applicable to a
number of microcomputers.

The Future

The microcomputer market will
continue to change. Manufacturers are
aiming many new products at the
business market and microcomputers
are now regularly advertised on the
financial pages of major newspapers
and are featured in radio promotions.

The new Apple IE and CBM pro-
ducts are definitely for the business-
man, not the "hacker." These business
users will require different levels of
support than the current users.

Another group of users emerging is
the consumers— the home market. The
Atari, VIC, and Intellivision are based
on pre-programmed packages which re-
quire no user modification or program-
ming. Anyone can use them, instantly!

We have some ideas which will be
implemented in MICRO over the com-
ing months. These include "bonus"
sections providing focused coverage of
particular topics such as graphics, pro-
gramming languages, games, printers,
disk systems, art, business, education,
and expanded coverage of the Apple,
PET/CBM, and other systems. We are
planning a MICROScan section which
will provide a systematic evaluation of
products within an area. We expect to
cover the new microprocessors which
may gradually supplant the 6502; as the
processors change, our readers will be
kept informed.

I am sure there are many other areas
in which MICRO can help serve its
readers. The staff of MICRO is very in-
terested in hearing from you. Please
write and let us know about your in-
terests, how your use of the micro-
computer is changing, and how we at
MICRO can continue to support your
efforts.

#■

Ytfj^ff

Robert M. Tripp
Editor/Publisher

About the Cover

PHOTO LIBRARY CATALOG

FLAGS: C ? ? 78 61

SUBJECT: TRAVEL

. HISTORIC

f TRAINS.

DESCRIPTION

PHOTO #

BY
IW

DATE
3/12/79

FORMAT

SANTA FE

A-6502-1

35MM

LITTLETON Nri

A-6502-2

l.W

8/20/78

35MM

MT. RUSHM0RE

B-6502-8

5/09/80

35MM

RIVERB0AT

K-65B2-5

9/19/79

35MM

BIG SUR

N-6502-3

5/31/80

35MM

PN.TiOTO

S-6809-7

1/17/71

3X4

IC CHIP

1-6889-2

12/12/72

4X5

WASHINGTON DC

1-1234-5

rir

11/11/77

3X4

CHELMSFORD Mfi

1-1234-7

5/05/77

4X5

Information Retrieval

The cover depicts an information retrieval
application in which a photographer with a
collection of many photographs needs to
select a subset of particular categories.
These could include black and white or col-
or; a slide, negative, print or other; where it
had been previously published; etc.
Categories dealing with subject matter
could be broken down to include
indoor/outdoor, people/scenic, day/night,
and others. A data base would consist of in-
dividual records with FLAGS and a portion
which would contain other information
about the photo for sorting purposes. For ex-
ample, the photographer could request
photos which are in color (C), scenic (S),
outdoor (O), and so forth, skipping

categories which he does not wish to select
by entering a question mark. He could fur-
ther select the fields of each record by speci-
fying key words which are to be matched
once a record has passed the basic FLAG
tests. The tests can be combined and can be
as complex as necessary.

Does this all sound very difficult? Not at
all. A system with all of these features, and
more, was implemented on a KIM-1 with
IK of RAM. It provided six tests on the
FLAGS and one test on each of six data
fields in the record. It provided up to 900
entries on a single 30-minute cassette tape.
The information retrieval process can be
applied to almost any data base.

(Photo by Loren Wright.)

No. 36 -May 1981

MICRO -The 6502 Journal

AMCftO

Letterbox

MICRO'S February editorial, "Too
Many Apples!" brought us a flood of
responses. Here ate just a few of the let-
ters offering comments and suggestions
on our Apple backlog problem.

Dear Editor:

In regard to the editorial "Too
Many Apples!" my solicited comment
as an avid reader of your magazine is
this: as an amateur futurologist, I
predict your editorial of February 1983
will be entitled: "Too Many PETs!"

It appears to me possible that the
$299 VIC 20 by Commodore may have
sold well over a million units by that
date and you will have an unwieldy ex-
cess of good articles on this machine!

George Earl

1302 South General McMullen

San Antonio, Texas 78237

Dear Editor:

I have been reading and enjoying
MICRO for several years, and have all
the issues since the beginning. I have
seen the magazine grow in size and
quality, and consider it my favorite of
several magazines I read regularly.

This letter is in response to your
editorial, "Too Many Apples!" My first
microcomputer was an AIM- 65, and I
enjoyed reading MICRO, because it
didn't ignore the board level computer.
Now I have an Apple n, and I can ap-
preciate your concern about giving
equal coverage to all the 6502-based
systems.

Of the six options suggested in the
editorial, allocating a larger portion of
MICRO to Apple, I believe, is fair since
it is the most popular 6502-based
computer, and by your own admission,
has the most articles available. The
addition of 16 to 32 extra pages is
something which is inevitable, if the
past growth of MICRO is any
indication.

I think the Apple is the best
6502-based micro on the market,
(that's why I bought itj, and I think it is
natural for it to receive extraordinary
coverage. Also, I still enjoy, and learn,
from the hardware articles which
appear in MICRO (such as Marvin
Dejong's article on the 6522), and if
you were to publish a separate
magazine only on the Apple, I probably
would subscribe to it, but would drop
MICRO, and would miss the 'hardware
stuff.' Since MICRO is the 6502 jour-
nal, it would be a shame to divide it in-
to a lesser pair of magazines.

Keep up the good work on MICRO,
and don't be afraid to 'overload' with
Apple stuff— there are a lot of Apples
out here!

Edward Janeczek
6121 Carnation Road
Dayton, Ohio 45449

Dear Editor:

I have been an avid reader of
MICRO since Issue #7, and it has never
been better than it is today. I'd like to
congratulate you on the vastly improved
appearance of the magazine. The typo-
graphy is far better than it used to be
before last December.

I own an Ohio Scientific C1P, and I
was interested in your February
editorial about your surfeit of Apple
articles. One of the reasons I like
MICRO so well is that there are a
number of articles every month that I
can use with my own computer. I
would hate to see MICRO become
devoted entirely to the members of the
Apple corps. Still, I have always felt
more of a kinship to the Apple and KIM
owners than to the PET owners, who
seem to dominate other magazines.

So what should MICRO do? Hard-
ware is interesting, particularly general
purpose "how I connected a DAC to
my 6522" material. General short 6502
software ("how to convert ASCII to
EBCDIC in seven bytes of code") is
usually interesting, but you shouldn't
include any listings that are more than
a page. Avoid "POKE 67 into location
$E5 on your Apple and see what hap-
pens!" articles. Don't assume that
everyone has dual disk drives and a
Diablo printer. Avoid large turn-key
type software for specific systems.
(Nobody out here really cares about
small business software, you know.
Some people think that computers-

small computers, that is— should be
useful for something, and we really
ought to be able to help the small
businessman drop $5,000 or $10,000 on
small computer hardware and a like
amount on software.) What we want to
read about is systems software, and
FORTH, and UNIX, and C, and bubble
memories, and Winchester disk drives
that cost less than $500, and color
graphics systems, and music syn-
thesizers, and Dragons and Dungeons,
and Ethernet, and good text editors,
and material like that.

John P. Sohl

20446 Orey Place

Canoga Park, California 91306

Dear Editor:

You backed me into a corner. When
I looked toward the right, I saw the en-
ticement to renew for another year at
the $15 rate. When I looked toward the
left, I saw an ever-expanding Apple
orchard.

I'm a single board man. I have a
KIM and an AIM. I enjoy that level of
computing. I'm not ignorant of the
capabilities of a larger system— I also
have a TRS-80 Level n. I get my
satisfaction out of making a $200 KIM
do the same things a $2000 Apple can
do (almost!).

In your editorial, you asked for
opinions. I look to MICRO for ASK
articles. I've been with you since Issue
#1. I've seen the larger systems come
down in price and increase in popu-
larity. The days of every computer hob-
byist knowing what a KIM is are gone.

Those days are gone, but your
readers, like myself, are not. I don't ask
for 100% ASK articles— that would be
unrealistic. What I do ask is that you
keep the same carefully planned
balance that you struck in Issue 33. If
you find yourself overloaded with ex-
cellent Apple articles, by all means,
publish them. But, go with the Apple
supplement idea— that looks best to
me. This assumes that others, like
myself, will continue to keep you fed
with good articles on the various other
systems. If that fails, you have no
choice other than to become the
"MICROApple."

Jody Nelis

132 Autumn Drive

Trafford, Pennsylvania 15085

(Continued on page 16)

MICRO - The 6502 Journal

No. 36 -May 1981

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No. 36 - May 1981

MICRO -The 6502 Journal

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MICRO - The 6502 Journal

No. 36 -May 1981

MacApple

This routine allows substitution
of unreserved control keys as
shorthand for commonly used
Integer BASIC commands. Since
It is table driven, extension to
Applesoft or machine language
is possible.

David Lubar

249 Loring Ave., Apt. 3

Edison, New Jersey 08817

The program "Applesoft Shorthand"
(23:5) was impressive. Here was a way
to shorten those long hours spent
thrusting two fingers at the keyboard. I
had several long programs to enter the
other night, but they were in Integer
BASIC. This left two choices; wait un-
til MICRO published what I needed, or
write it myself. I took the second op-
tion. The program (minus the one bug
which kept me up until 6:30 a.m. on a
bleary Sunday) is described in the
following article. Since I didn't have
the locations of Integer's keywords, I
took another approach, making a table
from which the keywords are printed.
While this lengthens the program, it
also gives the program multilingual
potential — by changing the table, you
can use it with Applesoft or even
assembly language.

Using MacApple

MacApple loads from $1000.$1131.
The table goes up to $10CF followed by
a $62 byte program. Turn it on with a
CALL 4383, off with a CALL 4393.
Once MacApple is turned on, any con-
trol key which is not reserved will pro-
duce a keyword. Using the $1000 area
allows the program to lie between a
BASIC program and the variable table.
This way, you can leave it in memory
while entering and modifying BASIC
programs.

How It Works

The table contains the ASCII values
of the keywords. The end of an entry is
signalled with a null character ($80).
With a range of 26 letters, eight
characters per letter seemed like a good
amount of storage. The CALL 4383
changes the pointers at $38, $39, caus-
ing the monitor to go to MacApple
instead of the normal KEYIN routine.
At the start of MacApple, the KEYIN
routine is duplicated in part, without
the portion that increments the ran-
dom number. If the ASCII value of the
character entered is less than $9B, it is
a control character. Other characters
are sent back to KEYIN at the point
where the strobe is reset. From there,
they follow the normal path into the
buffer and onto the screen.

For control characters, a check has
to be made. Certain of these characters
should be left alone. For example,
control-M is the carriage return. This,
obviously, is needed. The front and

back arrows, controls U and H, were
also left alone. The other reserved con-
trol characters, B, C, D, and X, aren't
essential, but I left them alone, giving
the user the option to do as he wishes.
Once you're in BASIC, control-B isn't
needed. Control-C can be replaced with
a JSR from the monitor. Its other func-
tion, stopping a program, can be re-
placed with a brute-force RESET,
though you lose the ability to see where
the program stopped. Control-D is left
free for disk users. Instead of control-X,
you can cancel a line by adding a syntax
error.

You can check for these reserved
characters by the series of CMP's and
BEQ's. The checks are written in
ascending order. The program can be
speeded up (for those of you who can
count microseconds) by placing the
most common ones (controls M, H,
and U] at the top of the series.

Once an input passes this far, the
heart of the program goes into action.
First, the ASCII value is reduced from a

Table 1

Control Key

Result

Control Key

Result

ASC("

reserved

COLOR 5

reserved

PLOT

PEEK

RETURN

POKE

SCRN(

GOTO

THEN

reserved

INPUT

VLIN

GOSUB

HLIN

CALL

reserved

LEN(

REM

reserved

DIM

Note: Though not all keywords could be paired with their initial letter, an

attempt was made to produce a meaningful relation. For example, to remember

that J produces

GOSUB, just

think of GOSUB as JSR. Pairs were placed

together when possible (VLIN,

HLIN and PEEK, POKEJ.

No. 36 - May 1981

MICRO -The 6502 Journal

range of $81-$9A to a range of $00-$19.
Next, this value is multiplied by 8 with
three ASL's. These steps result in a
pointer to the character table. The
pointer is put into the Y register. The A
register is loaded with DATA, Y, getting
the first character for the desired
keyword. This character is compared to
$80. If it isn't $80, the character is
stored in the input buffer and sent to
the screen through the COUT1 routine
in the monitor |FDF0).

Note: No check is made to see if the
buffer has been filled. If a keyword puts
the buffer count too high, it will do a
hatchet job on the line and begin filling
the buffer from the start. Just keep this
limitation in mind and there will be no
problems.

After this, Y is incremented to point
to the next character in the table, and X
is incremented to point to the next
location in the buffer. Once the
keyword has been output, there is an
$80 in the A register. It might seem
that there would be no harm in sending
this null character out. In most cases,
this is true. But it could cause prob-
lems. For example, the ASC function
returns the value of the first character
after the quote. If $80 is sent out, it
won't be on the screen, but it will
become the argument for the ASC func-
tion. No matter what letter follows,
BASIC will return a decimal value of
128. To avoid this, the routine clears
the strobe, resets the cursor, and goes
back for the next input. If the cursor
isn't reset with LDY 24, strange things
happen. Try deleting this command.
Then, in BASIC with MacApple turned
on, enter the control keys for PRINT
followed by ASC(". (Control-P,
control-A.) The next key entered will
cause the T in PRINT to turn into a @.

The Table

Changing the keywords, either for
Integer or for other languages, is sim-
ple. You can either step through the
monitor or go directly to an entry. To
step through the monitor, enter FFF
and hit RETURN. Hitting RETURN
again will cause a list of bytes
$1000-$1007. These locations contain
the keyword printed by control-A. Each
RETURN will advance to the next let-
ter, up to $10C8-$10CF, which is the
location for control-Z. If you don't feel
like stepping through. the monitor, use
the following method. Take the letter

0800

j. ******************

0800

't *

0800

,. *

MACAPPLE

0800

1* BY

DAVID LUBAR

0800

•: *

0800

.******************

08.00

. *

0800

. *

0800

EPZ $24

0800

BASL

EPZ $28

0800

KSWL

EPZ $38

0800

KSWH

EPZ $39

0800

EQU $200

0800

DATA

EQU $1000

0800

KBD

EQU $C000

0800

STROBE EQU $C010

0800

KEY1

EQU $FD2B

0800

COUT1

EQU $FDF0

0800

;

10D0

ORG $10D0

10D0

OBJ $800

10D0

10DO

•DATA

GO FROM S1000-S10CF

10DO

10D0 2C00C0

START

BIT KBD

;KEY DOWN?

10D3 10FB

BPL START

;NO

10D5 9128

STA (BASL)

;YES. REPLACE CURSOR

10D7 AD00C0

LDA KBD

;GET CHARACTER

10DA C99B

CMP #$9B

/CONTROL CHARACTER?

10DC 9003

BCC MAIN

;YES

10DE 4C2BFD

BACK

JMP KEY1

;NO. OUTPUT IT

10E1 C982

MAIN

CMP |$82

,-CONTROL-B?

10E3 F0F9

BEQ BACK

;YES

10E5 C983

CMP #$83

;CONTROL-C?

10E7 F0F5

BEQ BACK

10E9 C984

CMP |$84

;CONTROL-D?

10EB F0F1

BEQ BACK

10ED C988

CMP #$88

;CONTROL-H?

10EF F0ED

BEQ BACK

10F1 C98D

CMP #$8D

;CONTROL-M?

10F3 F0E9

BEQ BACK

10F5 C995

CMP #$95

;CONTRQL-U?

10F7 F0E5

BEQ BACK

10F9 C998

CMP #$98

/CONTROL-X?

10FB F0E1

BEQ BACK

10FD 38

SEC

.•REDUCE VALUE TO A RANGE

10FE E981

SBC #$81

; OF $00-$19

1100 0A

ASL

.•MULTIPLY BY 8

1101 0A

ASL

1102 0A

ASL

1103 A8

TAY

1104 B90010

LOOP

LDA DATA.Y

;GET TABLE ENTRY

1107 C980

CMP #$80

;END OF ENTRY

1109 F00B

BEQ BACK1

;YES

HOB 9D0002

STA IN,X

;N0. PUT CHARACTER IN BUFFER

HOE 20F0FD

JSR COUT1

/PRINT CHARACTER

1111 E8

INX

;INC BUFFER POINTER

1112 C8

INY

;INC TABLE POINTER

1113 4C0411

JMP LOOP

;DO IT AGAIN

1116 2C10C0

BACK1

BIT STROBE

;CLEAR KEYBOARD STROBE

1119 A424

LDY CH

/RESET CURSOR VALUE

111B 4CD010

JMP START

/CURE FOR DEAD BATTERIES?!

HIE EA

NOP

/EXTRA BYTE SO CALL FROM BASIC

111F

/WILL

BE AN EASY NUMBER

111F

(TO REMEMBER

111F

;CALLS

FROM BASIC

ENTER HERE

111F

111F A9D0

LDA # START

/SET VALUES FOR INDIRECT JUMP

1121 8S38

STA KSWL

1123 A910

LDA /START

1125 8539

STA KSWH

1127 60

RTS

1128 EA

NOP

/ANOTHER FILLER BYTE

1129 A91B

OFF

LDA ($1B

112B 8538

STA KSWL

11 2D A9FD

LDA »$FD

112F 8539

STA KSWH

1131 60

RTS

MICRO - The 6502 Journal

No. 36 -May 1981

you want and subtract 1 from its loca-
tion in the alphabet. Then multiply
this by 8. Add this, in hex, to $1000.
(Congratulations, you have just per-
formed a machine-language subroutine
in your head. ) That value gives the start
of the table for the desired letter.

Once you've found the starting
point, enter the ASCII values for the
desired keyword, followed by an $80. If
you don't have an ASCII table, use the
ASC function from BASIC, then con-
vert the number to hex. For those of
you who are lazy, I've included an
Integer BASIC program which con-
structs keyword tables in listing 1.

While the op codes for assembly
language are only three letters long,
you could save some typing by putting
together a table which included the
leading and trailing spaces and other
special characters. For example,
(space)LDA(space)#, for immediate
commands could be printed with one
control character.

Modifications

Relocating the program isn't dif-
ficult. Only a few changes are needed.
The JMP LOOP and IMP START are the
only jumps which refer to the program.
The value of DATA would have to be
changed, as would the values set by the
ON portion.

Final Notes

The pointers to the KEYIN routine
cannot be reset in the direct mode. Sup-
pose, for example, you change the lo
byte with POKE 56,NN. So far, there is
no problem. But as soon as you hit
RETURN, the monitor will go to the in-
put routine. When it hits the indirect
jump to KEYIN, it will find a value
with a new lo byte and an old hi byte.
Unless you are incredibly lucky, this
new value will not be one which has
anything to do with input. To see this
in action, enter POKE 56,7. (You can
reset the pointers with a line from
BASIC since the monitor won't look
for input during execution. ]

Disk users will have to add a CALL
1002 after turning MacApple on or off.

Finally, if you use the front or back
arrow immediately after a keyword, a
@ will appear on the screen. This can
be removed with the space bar.

I hope this program will save you
some time and effort.

Table 2: Keyword table.

1000 —

1008 —

1010 —

1018 —

1020 —

1028 —

1030 —

1038 —

1040 —

1048 —

1050 -

1058 —

1060 —

1068 —

1070 -

1078 —

DC)

1080 —

1088 —

1090 -

1098 -

10A0 —

10A8 —

10B0 —

10B8 —

10C0 —

10C8 -

10 DIM A$(26),B$(10)

20 A$="ABa}EPGHIJKLMNOPQRSTUVWXYZ"

30 FOR 1=0 TO 25

40 PRINT "ENTER KEYWORD FOR CONTROL ";A$( 1+1,1+1)

50 INPUT B$

60 IF LEN(B$)>7 THEN 40

70 FOR J=0 TO LEN(B$)-1

80 IF LEN(B$)<1 THEN 110

90 POKE 4096+8*I+J, ASC(B$(J+1,J+1) )
100 NEXT J

110 POKE 4096+8*I+J,128
120 NEXT I: PRINT "DONE": END

JVICftO

No. 36 - May 1981

MICRO - The 6502 Journal

* £T * :

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To subscribe, send your name and address to Dr. Dobb's Journal,
Department V4, Post Office Box E, Menlo Park, CA 94025.

We'll bill you.

«l

MICRO - The 6502 Journal

No, 36 -May 1981

KIM/SYM
Home Accounting System

This program illustrates a very
simple and basic application for
a personal computer in the
home that requires a minimum
of hardware to implement.

Robert Baker
15 Windsor Drive
Atco, New Jersey 08004

This article was originally written /or
the KIM but will also run on the SYM
with the included routines.

After acquiring a KIM-1 micro-
computer, this simple program was
written to help justify its existence in
our home. The program was designed
to do the bookkeeping for our family
budget but could easily be used for
many other applications.

My goal was to write a program that
would not require any additional hard-
ware besides the very basic system
containing a KIM-1 module, power
supply, and cassette recorder. Thus,
the program uses the on-board
keyboard for all input, and the
7-segment displays for all output by
means of two of the monitor sub-
routines in ROM. The positioning of
the 7-segment displays makes them
ideal for displaying monetary values
with a small space between the
"dollars" digits and the "cents" digits,
but the program can also be used for
various other applications, such as a
parts inventory.

The program itself resides in page 2
(Loc. 0200-02FF) of RAM and uses the
first locations of page zero for working
storage as shown in the program
listing. Page 3 |Loc. 0300-03FF) of RAM
is used to store the balances of each
account with three bytes per account.
The first three locations of page 3 are
reserved for account #0 which is the
overall total of all existing accounts.
The remaining space of page 3 may be

Table 1:

Keyboard Commands (# = any decimal number 0-9)

Input

Operation/Display

##A

Set account number '##'
Display reads 'AAAA ##'

(no input) A

Display current account number.
Display reads 'AAAA ##'

(no input) +

Increment account number & display new number.
If at last account "wrap" to account #0.
Display reads 'AAAA ##'

B (any time)

Display balance of current account.
Display reads '######'

#### ##C

Credit current account & display new balance.
Display reads '######'

#### ##D

Debit current account & display new balance.
Display reads '######'

If current balance is less than amount to be deducted, item
will be disregarded and display will read 'EEEE EE'

0800

*******************

0800

oeoo

* KXM + 1 - ?

0800

•

0800

* BY FCBFRT BAKEF

0800

*******************

0800

ffl

EPZ $F9

;LSD 7-SEGMFNT DISPLAY

0800

]

=OINTL EPZ SFA

;raiXLE 2 DIGITS IN DISPLAY

0800

]

=OINTH EPZ $FB

,-MSD IN DISPLAY

0800

3CANDS EQU $1F1F

;SCAN DIGITS DISPLAY & LOCK FOR

INPUT

0800

(

3FTKEY ECU $1F6A

;READ KEYBOARD INPUT

0800

=TR

EPZ $00

;TARLF POINTER

0800

W3CT

EPZ $01

[CURRENT A0CT #

0800

INFLG

EPZ $02

; INPUT FLAG

0800

TORK

EPZ $03

.-WORKING STORAGE

0800

0200

ORG $200

0200

OBJ $800

0200 A900

START

LTA #$00

;IMIT ACCT# =

0202

85F9

SETA

STA IMF

;SFT ACCT*

0204 8501

STA ACCT

0206

29F0

SFTPTF AND #$F0

;SFT POINTER -

0208 4A

LSR

rCONVERT ACCT#

0209

LSR

; TO BINARY &

020A 8503

STA WORK

.-MULTIPLY BY 3

020C 4A

LSR

020D

8500

STA PTR

020F A501

LEA ACCT

0211

38.

SFC

0212

E503

SPC WORK

0214 E500

SBC PTR

No. 36 -May 1981

MICRO - The 6502 Journal

used as required for up to 84 individual
accounts. The maximum number of
accounts is determined by the value in
location 02BA, which should be one
greater (decimal) than the highest
account number desired.

After hand-loading the program the
first time, be sure to clear all locations
of page 3 that are to be used for storage
of the account balances (Loc. 0300 to
0302 + (3 * #accounts) ). Also, don't
forget to set the highest account
number plus one in location 02BA. The
locations on page zero are initialized
by the program so there is no need to
set (or save) these.

When you are ready to run, load
address 0200 and depress "GO". The
display should read 'AAAA 00' to
indicate proper initialization with the
current account number equated to
zero. You're now ready to use the pro-
gram as desired. Table 1 gives a
complete description of each of the
keyboard controls; keys 0-9 are used for
input values and keys A,B,C,D, and +
are used for control.

Each time a value is added to
|credit) or subtract from (debit) an
individual account, it is also added/
subtracted to account #0 to keep a run-
ning total of all account balances. This
provides a simple method of comparing
your checking and savings accounts
with your budget balance. To keep
account #0 valid, the program will not
allow you to credit/debit account #0
directly. Also, if you try to debit an
account with an amount greater than
its current balance, the entry will be
disregarded and the display will read
'EEEE EE' to indicate the error.

After each session of running the
program simply store the program on
cassette following the standard pro-
cedures, locations 0200 to (0302 + (3 *
#accounts) ). This will save the current
account balances plus the program
itself. Then, the next time you want to
run the program, simply load from
cassette and start at location 0200.
Alternately, you can save pages 2 and 3
separately to conserve space on
cassette, or to allow more program
flexibility for specific applications.

0216 8500

STA PTK

0218 0A

ASL

0219 6500

ADC PTR

021B 8500

STA PTR

021D A9AA

LTA #$AA

; DISPLAY A'S

021F 85FA

CHRS

STA POINTL

;LOAD DISPLAY SPECIAL CHARACTERS

0221 85FB

STA POINTH

0223 A901

CLFLG

LTA #$01

;CLEAR INPUT FLAG

0225 8502

STA INFLG

0227 201F1F

DSPLY

JSR SCANTS

; DISPLAY DATA

022A

;F0R SYM, SUBSTITUTE CODE AT $106

022A DOFB

BNE DSPLY

022C 201F1F

INPT

JSR SCANTS

;WAIT FOR INPUT

022F

,-FOR SYM, SUBSTITUTE CODE AT $106

022F FOFB

BEQ INPT

0231 206A1F

JSR GETKEY

;RFAD KFY

0234

;FOF. SYM, SUBSTITUTF C0DF AT $133

0234 C90A

CMP #$0A

; DIGIT?

0236 1018

BPL CNTL

; BRANCH IF CONTROL KEY

0238 A0O4

LTY #$04

;SFT NORMAL SHIFT COUNT

023A C602

DEC INFLG

; FIRST INPUT?

023C D002

BNE SHFT

023E A018

LDY #$18

;YES, SET SHIFT COUNT TO CLEAR DISPLAY

0240 06F9

SHFT

ASL INH

; SHIFT DIGITS

0242 26FA

ROL POINTL

0244 26FB

RQL POINTH

0246 88

DFY

0247 D0F7

BNF SHFT

0249 45F9

EOR INH

;ADD NEW DIGIT

024B 85F9

STA INH

; TO DISPLAY REGISTER

024D 4C2702

JMP DSPLY

;GET NEXT KEY

0250 C90B

CNTL

CMP #$0B

;WANT BALANCE?

0252 D00F

BNF INCHK

0254 A400

BAL

LEY PTR

;YES, GET POINTER

0256 A202

LDX #$02

0258 B90203

MEAL

LTA TBLH.Y

,-MDVE BALANCE

025B 95F9

STA INH,X

; TO DISPLAY

025D 88

DEY

025E CA

DEX

025F 10F7

BPL MEAL

0261 D0C0

LINK

BNE CLFLG

jCLFAR FLAG & WAIT

0263 C602

INCHK

DEC INFLG

;ANY INPUT?

0265 F03E

BEQ GETA

0267 C90A

CMP #$0A

;YES, NEW ACCT*

0269 DOM

BNE CRTT

026B A5F9

LDA INH

;YES, GET NEW ♦

026D- 104A

BPL CHKA

; CHECK IT

026F A000

CRDT

LDY #$00

0271 C400

CPY PTR

,-AOCT #0?

0273 F0B2

BFO DSPLY

; ERROR, CAMNOT CR/DB ACCT #0

0275 C90C

CMP #$0C

; CREDIT ACCOUNT?

0277 D00A

BNE DBT

0279 20C002

JSR ADD

;YES, ADD TO ACCOUNT

027C A400

LDY PTR

027E 20C002

JSR ADD

;ADD TO ACCOUNT

0281 F0D1

BFO BAL

;SHCW BALANCE

0283 C90D

DBT

CMP #$0D

;DEBIT ACCOUNT?

0285 DOAO

BNE DSPLY

;NO, DISCARD KEY

0287 20C902

JSR SUB

,-YES, SUB FROM ACCOUNT #0

028A BOOB

BCS DECK

; NEGATIVE RESULT?

028C A000

DBFRR

LTY #$00

;YES, ADD # BACK

028E 2OCO02

JSR ADD

0291 A9EE

LDA #$EE

rPUT F'S IN DISPIAY

0293 85F9

STA INH

0295 C088

BNE CHRS

;SHCW ERROR (EEEE EE)

0297 A400

EBOK

LEY PTP,

0299 20C902

JSR SUB

;SUB FROM ACCOUNT

029C B0B6

BCS BAL

;SHCW BALANCE IF O.K.

029E A4O0

LDY PTR

;ADD # BACK IF ERROR

02A0 20C002

JSR ADD

02A3 F0E7

BEQ DBERR

;ADD BACK TO ACCT S. SHOW ERROR

02A5 C90A

GETA

CMP #$0A

; DISPLAY ACCOUNT #?

02A7 DO05

BNE NEWA

02A9 A501

LDA ACCT

;YES, GET #?

02AB 4C0202

SHCWA

JMP SETA

;SHOW IT

02AE C912

NEWA

CMP #$12

rINC ACCOUNT #?

02B0 DOAF

BNE LINK

;NO, CLEAR INPUT FLAG & WAIT

02B2 A501

LDA ACCT

;YES, GET ACCOUNT #

02B4 F8

SED

;GO TO DECIMAL MODE

02B5 18

CLC

;CLEAR CARRY

02B6 6901

ADC #$01

,-INC #

02B8 D8

CLD

;BACK TO BINARY MODE

02B9 C9

CHKA

BYT $C9

,- 'CMP'-- CHECK ACCOUNT #

02BA 00

BYT $00

;LAST ACCOUNT #1 + 1 GOES HERE

02BB

MICRO -The 6502 Journal

No. 36 -May 1981

02BB

02BB 30EE

BMI SHOWA

;O.K. , SHOW IT

02BD 4CCI002

JMP START

.•SET TO IF TOO LARGE

02C0

•ADD/SUBTRACT ROUTINE

02C0

02C0 A918

ADD

LDA #$18

; 'CLC'-SET INSTR FOR ADD MODE

02C2 8DDA02

STA INSTR1

02C5 A975

LDA #$75

.-'ADC'

02C7 D007

BNE STINST

02C9 A938

SUB

LDA #$38

;SET INSTR FOR SUB MODE

02CB 8DDA02

STA TUSTR1

02CE A9F5

LDA #$F5

02D0 8DDE02

STONST STA INSTR2

02D3 A203

LDX #$03

;SET LOOP COUNT

02D5 8603

STX WDFK

02D7 A20O

LDX #$00

;SET INDEX X

02D9 F8

SEE

;DECIMAL MODE

02DA 38

INSTR1

SEC

•CLEAR/SET CARRY

02DB B900O3

MATH

LDA TBLL.Y

• GET DIGITS

02DE F5F9

INSTF2

SBC TNH.X

.-ADD/SUBTRACT

02E0 990003

STA TBLL.Y

;ST0RE RESULT

02E3 E8

INX

,-TNC INDEX REGISTERS

02E4 C8

02E5 C603

DEC WORK

;DEC LOOP COUNT

02E7 D0F2

BNE MATH

.•CONTINUE

02E9 D8

CLD

; RESET BINARY MODE

02EA 60

RTS

.•RETURN

02EB

.•BEGINNING OF ACCOUNT DATA

(3 BYTES/ACCOUNT)

02EB

.-MAXIMUM OF 84 INDIVIDUAL ACCOUNTS + ACCOUNT #0

02EB

0300

ORG $300

0300

CBJ $800

0300

•

0300 00

TBLL

BYT $00

;ACC0U»T —LSD

0301 00

BYT $00

0302 00

TBLH

BYT $00

.•ACCOUNT — MSD

0303

;

0303 00

BYT $00

.-ACCOUNT 1 —LSD

0304 00

BYT $00

0305 CO

BYT $00

rACCOUNT 1 —MSD

0306

0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800
0800

The following routines, provided by
Nick Vrtis, originally appeared in his
article "The First Book of KIM on a
SYM" (MICRO 14:35) and reappeared
in The Best of MICRO Volume 3.
These routines allow you to use the
program on a SYM.

BY NICK VRTIS

************************

SYrt-1 VERSIONS OF *

VARIOUS KDt ROUTINES *

************************
*

FOR FURTHER INFORMATION CONSULT THE
ORIGINAL ARTICLE WHICH APPEARED IN:
MICRO 14:35
BEST OF MICRO VOL. Ill P. 63

TRANSO

PZSCR

POINTH

POINTL

INH

SYM PAD

HttlPBD

SVMDIS

SXMSCA

EQU $0137
EPZ $FC
EPZ $FB
EPZ $FA
EPZ $F9
EQU SA400
EQU SA402
EQU $A640
EQU $8906

iTRANSIATE TABLE LESS OFFSET $11
PAGE ZERO SCRATCH LOCATION
EXECUTE RAM POINTER HIGH
EXECUTE RAM POINTER LOW

iTERMINAL CHARACTER INPUT

[OUTPUT PORT A ON 6532

lOUTPUT PORT B ON 6532

DISPLAY BUFFER

LED OUTPUT DISPLAY BUFFER

Charge MICRO
and MICRO Books!

MICRO now accepts
VISA and Mastercard.
Credit card holders
around the world can
now order subscriptions
and books by phone or
mail.

Call (617) 256-5515
between 9:00 A.M. and
5:00 P.M. and say
"Charge it!"

Or mail your order with
your credit card name,
number, and expiration
date to:

Order Department

MICRO

P.O. Box 6502

Chelmsford, MA

01824

International Orders

If you are outside the U.S.,
you may pay by:

1. VISA or Mastercard

2. International
Money Order

We no longer accept bank
drafts from foreign
banks— even if the funds
are drawn on an account
in a U.S. bank! The rising
bank charges now make
payment by this method
prohibitive.

No. 36 -May 1981

MICRO - The 6502 Journal

Letterbox (continued from page 6)
Dear Editor:

I'm cheating, really... with regard to
your "Too Many Apples!" editorial....
You asked for feedback from readers,
and I'm not a regular MICRO reader.

I bought your February issue just for
the "In the Heart of Applesoft" article.
MICRO is a quality publication, but
there just isn't enough Apple-related
material to justify my subscribing.

I think I might be fairly typical of
the sort of reader who would buy
MICRO (or its Apple edition) on a
regular basis if there were enough
Apple coverage.

Good grief— thousands of us have
kilobucks invested in Apple (it's the
kind of computer that attracts in-
telligent laymen— no wonder so many
articles of high quality are submitted!).
With Pascal, I can tackle projects that
are light years beyond the scope of
KIM, SYM, et. al. and I'm hungry for
reading material!

As far as I'm concerned, you can
publish just one more article for those
bare-board, skinflint, kitchen table
time- wasters— "How to Convert Your
KIM-1 Into a Dedicated Coffee Per-
colator." That's it— the final article!

Given the choice of publishing a
magazine for the relatively well-heeled
and serious users of what may well be
the "Model A" of computing versus
publishing one for a minority of im-
poverished assembly language hob-
byists, it surprises me that you resist
the opportunity to publish more Apple-
based articles.

Where will KIM, SYM, PET and
AIM be in ten years? Apple, and its pro-
geny, might well dominate the world of
microcomputing by that time. Will
MICRO ride the bandwagon or drag its
heels? The choice is yours!

Please don' t publish my name or ad-
dress. I don't want my Apple stolen!

Editor's Note: Beginning in June,
MICRO will be expanding to include
more Apple articles each month. We
thank all who responded to the "Too
Many Apples!" editorial.

0800

SYMKEY EQU $8923

•CHECK FOR ANY KEY DCWN

0800

SYMLRN EQU S892C

DETERMINE KEY PRESSED

0800

SYMSEG EQU $8C29

;LED SEGMENT CODES

0800

0100

ORG $100

jOUT OF THE WAY ON STACK PAGE

0100

OBJ $800

0100

)sYM-l VERSION OF KIM SCAND

& SCANDS ROUTINES

0100

0100 A000

SCAND LDY #$00

ENTER HERE TO GET BYTE

0102 B1FA

LDA (POINTL), Y

ADDRESSED BY POINTL

0104 85F9

STA INH

AND MOVE IT TO INH AREA

0106

0106 A000

SCANDS LDY #$00

ENTER HERE IF INH ALREADY STORED

0108 A5FB

LEA FOINTH

POINTH FIRST TO DISPLAY BUFFER

010A 201A01

JSR SPLITP

010D A5FA

LEA POINTL

THEN DO POINTL

010F 201A01

JSR SPLITP

0112 A5F9

LDA INH

■LAST, BUT NOT LEAST, DO INH

0114 201A01

JSR SPLITP

0117 4C0689

JMP SYMSCA

■SET SYM MONITOR LIGHT & RETURN

011A

011A 48

SPLITP PHA

SAVE ORIGINAL

01IB 4A

LSR

ON STACK FOR LATER

011C 4A

LSR

SHIFT HI HALF TO LO HALF

011D 4A

LSR

011E 4A

LSR

WHICH IS 4 BITS DCWN

011F AA

TAX

PUT INTO X AS AN INDEX

0120 BD298C

LEA SYMSEG,X

GET APPROPRIATE SEGMENT CODE

0123 9940A6

STA SYMDIS,Y

AND PUT INTO DISPLAY BUFFER

0126 C8

INY

BUMP Y FOR NEXT BYTE

0127 68

PIA

NCW GET ORIGINAL VALUE BACK

0128 290F

AND #$0F

KEEP ONLY LOW ORDER 4 BITS

012A AA

TAX

AND REPEAT SEGMENT PROCESS

012B BD298C

LEA SYMSEG, X

012E 9940A6

STA SYMDIS,Y

0131 C8

INY

INCLUDING BUMP FOR NEXT BYTE

0132 60

RTS

AND RETURN

0133

;SYM-1 VERSION OF GETKEY SUBROUTINE

0133

0133 202C89

GETKEY JSR SYMLRN

■GET SYM VERSION OF THE KEY

0136 D003

BNE KEYDWN

BRANCH IF ANY KEY IS DCWN

0138 A915

GKNCNE LDA #$15

ELSE SET TO KIM NO KEY DCWN

013A 60

RTS

AND RETURN

013B 8A

KEYDWN TXA

X HOLDS INDEX INTO ASCII TABLE

013C C911

CMP #$11

NEED TO FUDGe'kEY VALUE?

013E 9007

BCC GKRTS

00-0F IS OK 10=AD(KIM)=CR(SYM)

0140 C916

CMP #$16

CHECK FOR OUT OF KIM RANGE

0142 B0F4

BCS GKNCNE

AND TREAT AS A 'NO KEY"

0144 AD3701

LDA TRANSO

ELSE TRANSLATE THROUGH TABLE

0147 60

GKRTS RTS

AND RETURN

0148

;

0148 12

TRANST BYT $12

, + , (Km) = '-/+'(SYM)

0149 11

BYT $11

•DA' (KIM)=NO KEY (KIM)

014A 15

BYT $15

SHIFT (SYM)=NO KEY (KIM)

014B 13

BYT $13

, G*(KDD = , GC/LP' (SYM)

014C 14

BYT $14

'PC' (KIM^'REG/SP" (SYM)

014D

;SYM-1 VERSION OF KIM KEYIN

SUBROUTINE

014D

014D 202389

KEYIN JSR SYMKEY

GET KEYBOARD STATUS

0150 D003

BNE KEYIN2

REVERSE ZERO FLAG

0152 A2FF

LDX #$FF

•KIM NOT ZERO— NO KEY— FF FOR LRNKEY

0154 60

RTS

0155 A200

KEYIN2 LDX #$00

•AND IS ZERO IF KEY IS DCWN

0157 60

RTS

0158

;SYM-1 VERSION OF KIM CONVD

ROUTINES $1F48 & $1F4E

0158

0158 84FC

CONVD STY PZSCR

SAVE Y IN SCRATCH AREA

015A A8

TAY

•MOVE NIBBLE OF A TO INDEX REGISTER

015B B9298C

LDA SYMSEG,Y

GET HEX SEGMENT CODES FROM TABLE

015E 8E02A4

DISPCH STX SYMPBD

SELECT THE DIGIT

0161 8D00A4

STA SYMPAD

•OUTPUT THE SEGMENT CODES

0164 A010

LDY #$10

KEEP IT LIT FOR A WHILE

0166 88

LIGHT DEY

0167 D0FD

BNE LIGHT

0169 8COOA4

STY SYMPAD

•TURN ALL SEGMENTS OFF FOR NEXT ONE

016C E8

1NX

;BUMP X TO NEXT DIGIT

016D A4FC

LDY PZSCR

•RESTORE THE Y REGISTER

016F 60

RTS

;AND RETURN

JUCftO

(

MICRO - The 6502 Journal

No. 36 -May 1981

/AlCftO

Challenges

By Paul Geffen

Last month's column may have left the
impression that Ohio Scientific pro-
vides very little documentation for its
products. This has been the case until
recently. The new management at OSI
is making an effort to improve the
quantity and quality of its documenta-
tion. This effort, started last year, is
still underway. Here is a report on the
results so far.

Last year OSI published a set of
revised User's Manuals for the C1P,
C4P, and C8P personal computers.
These were a big improvement over the
previous versions. The new User's
Manuals look better, contain more in-
formation, and are much more reliable
than the old ones. They also include
illustrations and photographs which
are valuable to the beginner. These
manuals cover the middle ground
because they assume a certain amount
of knowledge about computers, but
contain limited detail about the inner
workings of the machines.

More recently, OSI has published
manuals for the novice as well as for
the more advanced user. For the
novice, there is now a series of five
Introductory Manuals, for the C1P,
C4P, C4PMF, C4PDF and C8PDF. I
have seen only the first of these; the
rest should be available by the time you
read this. These manuals will be in-
cluded with the computers, along with
the User's Manual. These Introductory
Manuals assume very little and are
designed for the beginner. They include
many photographs and provide detailed
instructions on how to set up the
machine and save programs.

The manuals also provide very little
general information about BASIC.
They serve to de-mystify the machine
and make it accessible to someone who
knows next to nothing about com-
puters. This approach is designed to
make OSI personal computers appeal to
the mass market, those people who
now form the fastest growing part of
the computer market.

Also for the beginner, OSI publishes
two introductory BASIC texts. The first
is Understanding Your Ohio Scientific
C1P and C4P, A Workbook of Program-
ming Exercises in BASIC by Keith

Russell and David Schultz. This book
covers all the capabilities commands
and keywords of OSI BASIC (with the
exception of the USR[X) function). The
book is limited to the BASIC language
and avoids machine level information
so as not to confuse the reader. It is also
written specifically for OSI machines
and contains information peculiar to
these machines, like how to get started
and what POKEs to use to change the
screen format.

The second BASIC text is BASIC
and the Personal Computer by T.A.
Dwyer and M. Critchfeld. This book is
four times as long as the one by Russell
and Schultz, and is much more detailed
as well as broader in scope. While the
former covers only the basics, the latter
includes chapters on applications like
word processing, games, art, simula-
tion, data structures, sorting and files.
In addition to providing an introduc-
tion to computers and the BASIC
language, Dwyer and Critchfeld cover
many of the possible applications of
personal computers. This book was not
written for OSI computers. It is a
general BASIC text for college courses
published by Addison-Wesley with a
special cover for OSI. Some of the
material here applies to other versions
of BASIC, but for the most part the
book is written for users of any
machine. Both texts assume very little
initially, but the one by Dwyer and
Critchfeld goes further and faster.

For BASIC programmers who want
to learn about machine language, OSI
publishes the 65V Primer, an introduc-
tion to machine code on the OSI per-
sonal computers. OS 65V is the
machine . level monitor program in
ROM which provides the most fun-
damental support for other programs
like BASIC. This book is also a good
introduction to 6502 assembly or
machine language programming. It
describes all of the machine instruc-
tions and contains many examples and
exercises. It does not assume any
knowledge of computers, but it helps to
be able to program in BASIC before
reading this book.

OSI has completed two new
reference manuals which I have not
seen but which should be available
shortly. One is a new and improved
BASIC Reference Manual and the other
is an Assembler/ Editor/ Extended
Monitor Reference Manual. I plan to
review these in a future column.

For the hardware expert or repair-
man, Ohio Scientific and Howard Sams
publish three detailed Servicing
Manuals for OSI personal [C1P and
C4P) and business computers (CH and
CHI). These contain block diagrams,

parts lists, schematics, photos of the
boards, and very little text. They are
essential for repairing the computers
and helpful when modifying the cir-
cuitry. These manuals assume the
reader has a good electronics
background, the ability to read
schematics, and a working knowledge
of digital electronics. The only item
mising from these manuals is a
schematic of the power supply, which
is represented as a "black box."

All of the above documentation is
available from OSI dealers, separate
from the computers. In addition to
these publications, OSI has expanded
its customer service department and its
programming staff. If you own an OSI
machine and have questions about
hardware or software, write to the
Customer Service department, 1333
South Chillicothe Road, Aurora, Ohio
44202, or call [216) 831-5600.

For the experienced assembly
language programmer who wants to
know everything about the internal
operation of the OS65D V3.2 disk
operating system, a complete com-
mented disassembly of OS65D V3.2 is
available from Software Consultants,
7053 Rose Trail, Memphis, Tennessee
38134. This book has been praised in
all the newsletters. I have just received
a copy and plan a full report in my next
column.

The C2-4P

This is a relatively old OSI personal
computer. It is no longer in production
but since there are quite a few of them
around it deserves mention. This
model has since been upgraded to the
C4P. The only differences between the
two are that the C2-4P has an older (rev
A) video display board without color,
and an older version of the CPU board
with fewer I/O lines. Other than that,
the only difference is the enclosure.
C2-4P software will run on the C4P and
most C4P software will run on the
C2-4P unless it requires the I/O ports
on the new CPU board.

A used C2-4P can be a very inexpen-
sive personal computer but it helps to
know how to maintain it. Schematics
for the older boards are not in the C4P
servicing manual but can be obtained
from OSI directly. (Write to Bill Con-
rad at Customer Service.) Despite its
age, this model is not obsolete. Much
software continues to be written on and
for this computer. And it can be con-
verted into a C4P by replacing the two
boards mentioned above.

No. 36 -May 1981

MICRO -The 6502 Journal

NIBBLE IS TBffilFK

(For Your Apple)

NIBBLE 18: The Reference for Apple computing!

NIBBLE IS: One of the Fastest Growing new Magazines in
the Personal Computing Field.

: 18: Providing Comprehensive, Usefuland
Instructive Programs for the Home, Small Business, and
Entertainment.

NIBBLE IS: A Reference to Graphics, Games, Systems
Programming Tips, Product News and Reviews, Hardware
Construction Projects, and a host of other features.

NIBBLE IS: A magazine suitable for both the Beginner and
the Advanced Programmer.

Each issue of NIBBLE features significant new Programs of Commercial Quality. Here's
what some of our Readers say:

- "Certainly the best magazine on the Apple II"

- "Programs remarkably easy to enter"

- "Stimulating and Informative; So much so that this is the first computer magazine I've
subscribed to!"

- "Impressed with the quality and content."

- "NIBBLE IS TERRIFIC!"

In coming issues, look for:

D Stocks and Commodities Charting □ Assembly Language Programming Column

□ Pascal Programming Column D Data Base Programs for Home and Business

□ Personal Investment Analysis □ Electronic Secretary for Time Management
D The GIZMO Business Simulation Game

And many many more!

NIBBLE is focused completely
on the Apple Computer systems.

Buy NIBBLE through your local
Apple Dealer or subscribe now with
the coupon below.

TryaMBBLE!

NOTE:

f-irsl Class or Air Mali is required tor all APO. r-PO and all foreign addresses
with Ihe following additional amounts Africa: North $32.00

- Europe $32.00 Central $43.00

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- South America $3Z00 Far East, Australia $43.00

- Middle East $35.00 Canada $18.00
All payments must be in U.S. funds drawn on a U.S. bank.

i) WHO by MICRO-SPARC . INC.. Lincoln. Mass OI77.V All rights reserved
'Apple II is a registered trademark of Apple Computer Company

nibble

Box 325, Lincoln, MA. OI773 (6I7) 259-97IO

I'll try nibble!

Enclosed is my $17.50 (for one year).
(Outside U.S., see special rates on this page.)

□ check □

Your subscription will begin with the next issue published after
receipt of your check/money order.

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MICRO - The 6502 Journal

No. 36 -May 1981

Jp\

More Output
from your Micro

Here is a simple way to add
extra output bits to your single
board microcomputer. This
technique will work on the AIM,
SYM, KIM and OSI Superboard
or C1P. The method is similar to
that used on the Apple II for
generating sound, and a
"random beeper" program
concludes this article.

H.H. Aumann
1262 Rubio Vista
Altadena, California 91001

The circuit in figure 1 provides an
independent output bit which can be
turned on and off under program

control with minimal effort and
without tying up your VIA. It consists
of one half of a 74LS107 dual JK flip-
flop connected to unused address
decode outputs from the computer. In
this case, the flip-flop is used to drive
an audio amplifier and a speaker to
provide sound output, but many other
applications are possible. For example,
the output bit could be used to control
a printer or other device.

This is how it works. All
microcomputers use decoders to divide
the 64K range of possible addresses into
more manageable units. Some of the
outputs from these decoders are not
used on the board and are available for

other purposes. Table 1 shows what
addresses are unused on each micro and
where the corresponding signals may
be found.

Two of these decoder outputs are
used to set and reset the flip-flop in
figure 2. Almost any flip-flop may be
substituted, as shown. The output of
the flip-flop is the new output bit. If all
you want to do is toggle the output
then the decode line may be connected
to the clock input of the flip-flop. In
this case only one address is needed for
access but you may not be able to tell if
the output bit is on or off. In the case of
sound output this is not important.

Figure 1

A+ 5V

decode output L ^ . ^, t ,
— 4— 0>CLK

14 1 Q13

CLR
J Q

/7&

74LS107

270K

4.7K

+ 5V

200/Z.F

tw rir

SPEAKER

No. 36 -May 1981

MICRO - The 6502 Journal

If you use the circuit in figure 2,
then a read from an address
corresponding to decode output 1 will
turn on the output bit, and a read from
an address corresponding to decode
output 2 will turn off the output bit.

The following BASIC program
generates random sound output on the
OSI Superboard. The machine language
program is relocatable and will run on
any machine by changing the byte at
$0226. The BASIC program must be
changed to load the machine code in a
convenient location. This is left to the
reader as an exercise.

Table 1

AIM

SYM

KIM

OSI

$8000 A- 18
$9000 A-19
$A0OO A-20

$1000 A-F
$1400 A-H
$1800 E-16
$1C00 A-J

$0400 A-C
$0800 A-D
$0C00 A-E
$1000 A-F

$D400 write U20 - 9
$D800 write U20 - 10
$D400 read U20 - 13
$D800 read U20 - 14

A - Application Connector
E - Expansion Connector

Note: U20 is a

i 74138 decoder

chip on the OSI model 600 CPU board.

Figure 2

decode output 1

REM SIM

REM FOR

FOR I =

POKE I,B

POKE 11,

REM SET

D = 256 *

POKE 546

REM SET

X = USR

DATA 17

DATA 8 ,

PLE TONE GENERATOR DEMO

OSI SUPERBOARD / C1P
548 TO 567: READ BI
I: NEXT : REM LOAD $224-237
36: POKE 12,2

ENTRY POINT FOR USR(l)
RND (1) :P = 256 * RND (1)
,P: POKE 547, D

PERIOD AND DURATION
(1) : GOTO 40

3,0,216,136,208,5,206,35,2,240
202,208,245,174,34,2,208,237,96

ORG

$0222

PERIOD

DFS

DURATN

DFS

AD00D8

SOUND

LDA

$D800

DO 03

LOOP

BNE

SKIP

CE2302

DEC

DURATN

F008

SKIP

BEQ

DONE

DEX

D0F6

BNE

LOOP

AE2202

LDX

PERIOD

D0EE

BNE

SOUND

DONE

RTS

PR
D

CK Q

control

output

CLR

decode output 2

74LS74

decode output 1

7476

MICRO - The 6502 Journal

JMCftO

No. 36 -May 1981

SOFTWARE FOR OSI

A JOURNAL FOR OSI USERS!!

"The Aardvark Journal is a bimonthly tutorial for OSI
users. It features programs customized for OSI and
has run articles like these:

1) Using String Variables.

2) High Speed Basic On An OSI.

3) Hooking a Cheap Printer To An OSI.

4) An OSI Disk Primer.

5) A Word Processor For Disk Or Tape Machines.

6) Moving The Disk Directory Off Track 12.

First year issues already available!
$9.00 per year (6 issues)

ADVENTURES

Adventures are interactive fantasies where you give the

computer plain English commands (i.e. take the sword,

look at the control panel.) as you explore alien cities,

space ships, ancient pyramids and sunken subs. Average

playing time is 30 to 40 hours in several sessions.

There is literally nothing else like them — except

being there yourself. We have six adventures available.

ESCAPE FROM MARS - Explore an ancient

Martian city while you prepare for your escape.

NUCLEAR SUBMARINE - Fast moving

excitement at the bottom of the sea.

PYRAMID — Our most advanced and most

challenging adventure. Takes place in our

own special ancient pyramid.

VAMPIRE CASTLE - A day in old Drac's

castle. But it's getting dark outside.

DEATH SHIP - It's a cruise ship - but it ain't

the Love Boat and survival is far from certain.

TREK ADVENTURE - Takes place on a

familiar starship. Almost as

good as being there.

NEW SUPPORT ROMS FOR BASIC
IN ROM MACHINES

C1S - for the C1P only, this ROM adds full
screen edit functions (insert, delete, change
characters in a basic line). Softwave selectable
scroll windows, two instant screen clears (scroll
window only and full screen), software chose of
OSI or standard keyboard format. Bell support,
600 Baud cassette support, and a few other
features. It plugs in in place of the OSI ROM.
NOTE: this ROM also supports video conversions
for 24, 32, 48 or 64 characters per line. Replaces
video swap tape on C1P model 2. All that and it
sells for a measly $39.95.

C1E/C2E for C1/C2/C4/C8 Basic in ROM ma-
chines. This ROM adds full screen editing, soft-
ware selectable scroll windows, keyboard correc-
tion (software selectable), and contains an ex-
tended machine code monitor. It has breakpoint
utilities, machine code load and save, block
memory move and hex dump utilities. A must for
the machine code programmer replaces OSI sup-
port ROM. Requires installation of additional
chip when installed in a C2 or C4. C1 installation
requires only a jumper move. Specify system
$59.95.

DISK UTILITIES

SUPER COPY - Single Disk Copier
This copy program makes multiple copies,
copies track zero, and copies all the tracks
that your memory can hold at one time —
up to 12 tracks at a pass. It's almost as fast
as dual disk copying, — $15.95
MAXIPROSS (WORD PROCESSOR) - 65D
polled keyboard only - has global and line edit,
right and left margin justification, imbedded
margin commands, choice of single, double or
triple spacing, file access capabilities and all the
features of a major word processor — and it's
only $39.95.

P.C. BOARDS

MEMORY BOARDS!! - for the C IP. - and they
contain parallel ports!

Aardvarks new memory board supports 8K
of 21 14's and has provision for a PIA to give a
parallel ports! It sells as a bare board for $29.95.
When assembled, the board plugs into the expan-
sion connector on the 600 board. Available now!

PROM BURNER FOR THE C1P - Burns single
supply 2716's. Bare board - $24.95.
MOTHER BOARD — Expand your expansion
connector from one to five connectors or use it
to adapt our C1P boards to your C4/8P. - $1435.

ARCADE AND VIDEO GAMES

GALAXIA one of the fastest and finest arcade
games ever written for the OSI, this one features
rows of evasive, hardhitting, dogfighting aliens
thirsty for your blood. For those who loved (and
tired of) Alien Invaders. — P.S. The price is a
giveaway. SPECI FY SYSTEM !
Cassette $9.95 - Disk $12.95

TIME TREK (8K) - real time Startrek action.
See your torpedoes move across the screen! Real
graphics — no more scrollina displays. $9.95
INTERCEPTOR C1P ONLY! An all machine
code program as fast and smooth as the arcades.
You use your interceptor to protect your cities
from hordes of enemy invaders. A pair of auto-
matic cannons help out, but the action speeds up
with each wave of incoming ships. The fastest
and most exciting C1P game yet.
C1P Cassette $19.95

MINOS — A game with amazing 3D graphics.
You see a maze from the top, the screen blanks,
and then you are in the maze at ground level,
finding your way through on foot. Realistic
enough to cause claustrophobia. — $12.95

SINGLE STEPPER /MONITOR

This is probably the finest debugging tool for
machine code ever offered for OSI systems. Its'
trace function allows you to single step through
a machine code program while it continuously
displays the A, X, Y and status registers and the
program and stack pointers. You can change any
of the registers or pointers or any memory loca-
at any time under program control. It takes well
under 1k and can be relocated anywhere in free
memory. It is a fine tool for ail systems — and
the best news of all is the extremely low price we
put on it. -Tape $19.95- Disk $24.95

FOR DISK SYSTEMS - (65D, polled key-
board and standard video only.)
SUPERDISK. Contains a basic text editor with
functions similar to the above programs and also
contains a renumberer, variable table maker,
search and new BEXEC* programs. The BEXEC*
provides a directory, create, delete, and change
utilities on one track and is worth having by
itself.- $24.95 on 5" disk - $26.95 on 8".

AARDVARK IS NOW AN OSI DEALER!

Now you can buy from people who can support
your machine.

- THIS MONTH'S SPECIALS -

Superboard II $279

C1P Model II 429

C4P 749

8K 610 board for C1P 269

Epson MX-80 printer with RS232 installed 595

. . . and we'll include a free Text Editor Tape
with each machine!

True 32X32 Video Mod Plans for C1P

(4 Chips $3 .00 Crystal Required)

$7.95

This is only a partial listing of what we have to offer. We now offer over 100 programs, data sheets, ROMS, and boards
for OSI systems. Our $1.00 catalog lists it all and contains free program listings and programming hints to boot.

Aardvark Technical Services • 1690 Bolton • Walled Lake, Ml 48088

(313)669-3110

SPACE

t :

implies run select me game moae Horn rive
including Reverse Gravity, and the battle begins
erate to place your shots--and escape into hypersp,
your opponent comes within range But be wary h
may circle out of sight and reappear on the oppos
the galaxy' (This is the classic MIT game n
especially for the Apple i

SUPER inuflsion

• Super Invasion is the original invasion game, with the original
moon creatures and faster action than any other invasion game.

• Features superb high resolution graphics, nail-biting tension and
hilarious antics by the moon creatures!

Self-running "attract mode" of operation for easy learning and
demonstrating of the game.

As good in every way as the famous Invaders arcade game.

High speed action ! • Sound effects!
Runs on the Apple II and the Apple II Plus

mutrn

Fifty-five aliens advance and shower you with lethal writhing
electric worms. As you pick off the aliens, one-by-one, they
quicken their descent. They whiz across the screen wearing away
your parapets, your only defense, coming closer and closer to
your level. Super invasion is the original invasion game with the
original moon creatures and faster action than any other invasion
game on the market.

Super Invasion is available for only $19.95 on cassette
(CS-4006) for a 32K Apple II. Space War is $14.95 on cassette
(CS-4009) for a 16K Apple II. Space War and Super Invasion are on
one disk (CS-4508) for a 48K Apple II for only $29.95.

Send payment plus $1.00 shipping and handling to Creative
Computing Software, P.O. Box 789-M, Morristown, NJ 07960. NJ
residents add $1.00 sales tax. Bankcard orders may be called in
toll free to 800/631-8112. In NJ call 201/540-0445.

sensational
software

creative

computing

software

MICRO - The 6502 Journal

No. 36 -May 1981

Applesoft Variable Dump

This handy debugging utility
presents you with a "DUMP" of
current variable values, for
Applesoft in ROM.

Scott D. Schram
1201GreenviewRd.
Collierville, Tennessee 38017

This program searches through the
memory used by ROM Applesoft and
prints all non-subscripted variables. It
can mainly be used as a debugging tool
to see what is going on inside a piece of
code. I chose not to print the array
variables because no great need for it
had come up. Also, array variable
storage is considerably more complex.
(See the Applesoft manual, p. 137.)

You may enter this program into
your assembler from the listing or key
it in at $4000 using the monitor. This
location is right in the middle of
memory and will rarely conflict with
the Applesoft unless you have a giant
program with lots of strings. Save the
program on disk (BSAVE VARIABLE
DUMP,A$4000,L$CE) or tape (*4000.
40CDW).

To use the program, stop execution
of an Applesoft program and load the
variable dump into memory. Then
CALL 16384. You may BRUN
VARIABLE DUMP from disk. See the
sample run. Any simple variables will,
work even if defined in the immediate
mode.

The screen may scroll too fast to
read, so hit any key to stop the listing.
Then hit any key to start it again.
When the program is done, it will
return to Applesoft.

0800

ROUTINE

TO DUMP ALL SIMPLE VARIABLES TO CURRENT

0800

OUTPUT DEVICE.

0800

SCOTT SCHRAM

0800

EQUATES

0800

VARL

EPZ

$69

APSOFT'S POINTER TO SIMPLE

0800

VARH

EPZ

$6A

VARIABLE STORAGE.

0800

ARRAYL

EPZ

$6B

APSOFT'S POINTER TO

0800

ARRAYH

EPZ

$6C

END OF SIMPLE STORAGE.

0800

P0INTL

EPZ

$06

POINTER TO

0800

P0INTH

EPZ

$07

CURRENT VARIABLE.

0300

SPL

EPZ

$9E

STRING PRINT POINTER.

0800

SPH

EPZ

SPL+$1

0800

LEN

EPZ

SPH+$1

LENGTH OF STRING TO PRINT.

0800

STROBE

EQU

$C010

KEYBOARD STROBE

0800

KB0ARD

EQU

$CO0O

KEYBOARD

0800

APPLESOFT EQUATES

0800

(SEE

APPLE ORCHARD MAR/APR 1980)

0800

3IVAYF

EQU

$E2F2

APSOFT'S INTERNAL NUMBER

0800

'HTFAC

EQU

$ED2E

HANDLING ROUTINES.

0800

10VEFM

EQU

$EAF9

0800

3UTD0

EQU

IDB5C

j PRINT CHAR. IN A REG.

0800

:rdo

EQU

$DAFB

; PRINT A CARRIAGE RETURN

0800

3UTSPC

EQU

$DB57

j PRINT A SPACE

0800

UPSOFT

EQU

$D43C

j APSOFT'S WARM START

0800

4000

ORG

$4000

4000

>TART:

4000

20FBDA

JSR

CRDO

PRINT A C.R.

4003

A569

LDA

VARL

MOVE BYTES

4005

8506

STA

P0INTL

FROM VARIABLE

4007

A56A

LDA

VARH

POINTERS INTO

4009

8507

STA

POINTH

MY POINTER

400B

A506 1

.OOP

LDA

POINTL

SEE IF

400D

C56B

CMP

ARRAYL

I AM AT TOP

4 OOF

DO 09

BNE

PRINT1

4011

A507

LDA

POINTH

CHECK HIGH BYTE

4013

C56C

CMP

ARRAYH

IF BOTH ARE EQUAL THEN NO MORE

4015

D003

BNE

PRINT1

SIMPLE VARIABLES LEFT.

4017

4C3CD4

JMP

APS0FT

DONE.

401A

DETERMINE THE TYPE OF THE

NEXT VARIABLE AND DISPATCH

401A

TO THE CORRECT. ROUTINE.

401A

'RINT1

401A

A000

LDY

#$00

401C

B106

LDA

(POINTL) ,Y

THE HIGH ORDER BIT OF THE

401E

3008

BMI

INTGER

NAME DETERMINES THE TYPE.

4020

I NY

4021

B106

LDA

(POINTL), Y

4023

1026

BPL

REAL

4025

4C6740

JMP

STRING

4028

tNTGER

4028

I NY

4029

B106

LDA

(POINTD.Y

WEED OUT FUNCTION NAMES.

402B

105B

BPL

NXTS1

402D

209940

JSR

PRINTN

INTEGER HANDLING STARTS HERE.

4030

A925

LDA

#$25

No. 36 -May 1981

MICRO - The 6502 Journal

Note: This program is written to
work with ROM Applesoft. To convert
to disk or cassette would require con-
siderable effort. If you want to convert
it you will have to figure out the
equivalent addresses in RAM Applesoft
and change the equates in the listing.

I welcome any comments. Please
send them to the address at the begin-
ning of the article and include a S.A.S.E
if you desire a reply.

LIST

10 AA = 98E + 05
20 R$ = "THIS IS A

TEST"
30 N% = 2341
40 RR = 12345
50 FOR I = TO 10:

NEXT I
60 END

]RUN

]BRUN VARIABLE DUMP

AA 9800000

R $ THIS IS A TEST

N % 2341

RR 12345

I 11

]A=34567.98
]BB%=-32767
]CC$-"MOOSE"
]DD==12324+98

]N%==1232

]BRUN VARIABLE DUMP

A 34567.98

BB% -32767

CC$ MOOSE

DD 12422

N % 1232

1032 205CDB

JSR

OUTDO

1035 2057DB

JSR

OUTSPC

4038 A002

LDY

#$02

403A B106

LDA

(POINTD.Y

; GET THE INTEGER

403C AA

TAX

403D C8

I NY

403E B106

LDA

(POINTD.Y

4040 A8

TAY

4041 8A

TXA

4042 20F2E2

JSR

GIVAYF

j CONVERT TO FLOATING POINT

4045 202EE0

JSR

PRTFAC

; PRINT IT.

4048 4C8540

JMP

NXTSIM

404B

REAL:

404B 209940

JSR

PRINTN

; REAL HANDLING STARTS HERE.

404E 2057DB

JSR

OUTSPC

4051 2057DB

JSR

OUTSPC

4054 A407

LDY

POINTH

4056 A506

LDA

POINTL

4058 18

CLC

4059 6902

ADC

#$02

405B 9001

BCC

CONT

405D C8

I NY

405E 20F9EA

C0MT

JSR

MOVEFM

; USE APSOFT INTERNALS TO

4061 202EED

JSR

PRTFAC

; DO THE DIRTY WORK.

4064 4C8540

JMP

NXTSIM

4067

STRING

4067 209940

JSR

PRINTN

406A A924

LDA

#$24

406C 205CDB

JSR

OUTDO

406F 2057DB

JSR

OUTSPC

4072 A002

LDY

#$02

4074 B106

LDA

(POINTD.Y

; SET UP THE POINTERS FOR

4076 85A0

STA

LEN

; STROUT SUBROUTINE.

4078 C8

I NY

4079 B106

LDA

(POINTD.Y

407B 859E

STA

SPL

407D C8

INY

407E B106

LDA

(POINTD.Y

4080 859F

STA

SPH

4082 20AD40

JSR

STROUT

j PRINT THE STRING.

4085

NXTSIH SETS THE VARIABLE

POINTER TO THE NEXT VARIABLE.

4085

4085 NXTSIM

4085 20FBDA

JSR

CRDO

4088 18 NXTS1

CLC

4089 A907

LDA

#$07

408B 6506

ADC

POINTL

408D 8506

STA

POINTL

408F 9002

BCC

CONT2

4091 E607

INC

POINTH

4093 20BD40 C0NT2

JSR

WAIT

4096 4C0B4O

JMP

LOOP

4099

PRINTN PRINTS THE NAME OF THE CURRENT VARIABLE.

4099

>RINTN

4099 A0O0

LDY

#$00

; INDEX=0

409B B106

LDA

(POINTD.Y

; GET FIRST LETTER

409D 205CDB

JSR

OUTDO

4OA0 C8

INY

; MOVE UP

40A1 B106

LDA

(POINTD.Y

; GET NEXT CHAR IN NAME

40A3 297F

AND

#$7F

40A5 D002

BNE

CONT3

; IF THIS IS A SINGLE CHARACTER

40A7 A9A0

LDA

#$A0

;NAME THEN PRINT A SPACE.

40A9 205CDB

:0NT3

JSR

OUTDO

40AC 60

RTS

40AD

STROUT PRINTS A STRING POINTED

40AD

TO BY SPL.SPH OF LENGTH LEN

40AD

STROUT

40AD A000

LDY

#$00

40AF C4A0 I

.OOP1

CPY

LEN

40B1 F009

BEQ

RTS1

40B3 B19E

LDA

(SPL).Y

40B5 205CDB

JSR

OUTDO

40B8 C8

INY

40B9 4CAF40

JMP

L0OP1

40BC 60

*TS1

RTS

40BD

WAIT

LOOKS AT THE KEYBOARD

40BD

TO SEE IF

A KEY WAS PRESSED.

40BD

IF SO, IT WAITS FOR A SECOND

40BD

KEY

TO BE PRESSED BEFORE

40BD

RETURNS.

40BD

40BD ADOOC0 I

(AIT

LDA

KBOARD

40C0 10FA

BPL

RTS1

40C2 AD10C0

LDA

STROBE

40C5 AD00C0 V

rfAITI

LDA

KBOARD

40C8 10FB

BPL

WAIT1

40CA AD10C0

LDA

STROBE

40CD 60

RTS

MICRO -The 6502 Journal

No. 36 -May 1981

/AlCftO

Microprocessors in
Medicine: The 6502

Jerry W. Froelich, M.D.

9 Brown Place

Woburn, Massachusetts 01801

Previously in this column we have not
discussed applications where the com-
puter helps in the "direct" manage-
ment of patient therapy. In this issue
we will describe a "PET" computer
which keeps track of patients' data who
are being treated with a blood anti-
coagulant called warfarin [ Coumadin].

Background

There are several medical condi-
tions where retarding of the rate at
which blood clots is necessary to pre-
vent further complications of the
disease. The drug warfarin is ad-
ministered to "slow down" the blood
clotting mechanism.

An example where anticoagulation
is necessary is in a disease called "Deep
Venous Thrombophlebitis" (DVT)
where blood clots form in the deep
veins of the legs. This condition is
potentially life threatening in that a
large blood clot may dislodge from the
leg, travel through the heart, and lodge
in the lung. If the clot is large enough it
may totally block the flow of blood to
the lungs resulting in shock or death,
due to asphyxiation.

Warfarin is used for the long-term
treatment of diseases, but warfarin
itself may be life threatening if ad-
ministered in incorrect dosages. If too
much drug is administered, blood
vessels may bleed spontaneously. If too
little, the clotting process won't be
"slowed down." Therefore, drug
dosage and drug breakdown (in the pa-
tient) are critical to the use of warfarin.
The predictable body metabolism of
the drug makes it safe to use as long as
the patient is monitored closely.

Model of Anticoagulation Theiapy

Dr. William F. Powers at the
University of Michigan has approached
anticoagulation therapy from the
systems point of view. Although he
was not the first to apply computer

techniques to this problem, he was the
first to use a microprocessor at the
"bedside" to guide the physician and
monitor anticoagulation therapy. The
next several paragraphs (which refer to
figure 1) discuss the algorithm used to
model anticoagulation therapy, talk
about the computerization of the
algorithm, and show the equations for
the dynamic model of anticoagulation
therapy.

G = -GKg + D[t) (1)

Q = G Kg - Ke Q (2)

P = Sm[l -F/F + Km] - KpP [3]

Where F approximately equal to 0.003
Q / Warfarin distribution volume
which is approximately equal to aQ.
Then,

P = Sm(l -Q/Q + K) -KpP (4)

Where K = Km / a

Figure 1: The basic equations for the
dynamic model of anticoagulation
therapy.

Equation (1) assumes that the rate
of absorption of warfarin from the in-
testinal tract (the drug is taken by
mouth) is proportional to the amount
in the intestine, G.

The warfarin dosage schedule is
described by the function D( + ). Equa-
tion (2) states that the instantaneous
rate of change of the amount of war-
farin in the body, Q, is given by the dif-
ference between the rate of absorption
from the intestinal tract and its rate of
metabolism, the metabolism being a
first order process.

Equation (3) states the rate of the
prothrombin complex activity, (p), a
blood clotting parameter that monitors
the extrinsic pathway of the coagula-
tion cascade and is equal to the dif-
ference between the rate of synthesis of
the complex and its rate of degradation.
The reduction in the rate of prothrom-
bin complex synthesis below the nor-
mal value (Sm) due to inhibition by
warfarin is given by a Michaelis-
Menter formulation, in which (F) is the
concentration of free warfarin and (Km)
the Michaelis constant.

The parameters Kg, Ke, Kp, and K
are subject-dependent parameters. One
of the goals of the program is to rapidly
reach estimates of the subject-

dependent variables from the direct
measurements of patient clotting time
(prothrombin time tests). Once these
parameters have been determined, the
initial dosage may be optimized for a
given patient. Subsequently, the pro-
gram will be able to monitor changes of
the patient's clotting time during the
maintenance phase of drag adminis-
tration (the daily dosage required to
keep the clotting time in the thera-
peutic range] .

Dr. Powers has analyzed three
methods (1) to calculate the patient-
dependent parameters from Kg, Ke, etc.
He also settled on a "tuned" extended
Kalman filter method because it was
accurate and it could compute the
results within a few minutes, whereas
other techniques require between 30
and 60 minutes of computer time per
case.

Overview of the Programs

Dr. Powers has written a series of
programs. The early programs were
mainly concerned about the simulation
of the anticoagulation kinetics and
estimation of the patient-dependent
parameters. An example of the graph
generated by the Kalman filter program
is shown in figure 2. This graph
displays both the measured and the
computed prothrombin complex ac-
tivities as a function of time. The
patient-dependent parameters are also
displayed at the top of the figure.

The most recently written program
is appropriately titled MAIN-
TENANCE. This program is menu-
driven and interacts with the user
promoting a better man-machine inter-
action. Figure 3 is an example of the
menu. When the program is initially
run the program requests various infor-
mation about the patient being
monitored: the patient's full name,
phone number, parameters, and general
comments. The program then requests
the most recent laboratory values of the
prothrombin complex activities. After
entering the measurements the pro-
gram can recommend a dosage and
follow-up period (figure 4) from as few
as four measurements.

After each patient's data has been
entered it can be saved on a floppy disk
so that when the patient returns for
another visit, the data file can be recalled.
The program also flags such conditions
as an abnormal response to therapy.
The data files can be backed up by
copying the disk.

No. 36 -May 1981

MICRO - The 6502 Journal

The program was not designed to
replace the physician, but rather to
assist the physician in the management
of patients. All recommendations
regarding therapy must be checked
against the physician's understanding
of the therapy. By managing the pa-
tients in this manner the computer and
physician check each other and there-
fore yield higher quality medicine.

Summary

The previous sections have described
how an inexpensive microcomputer
such as the Commodore PET 2001 can
be utilized with modem techniques to
rapidly assess therapy and recommend
dosages for patients receiving an-
ticoagulation therapy. The programs
have been written in BASIC and the use
of the PET computer is straightforward.
Therefore, it requires only a matter of
hours to teach medical personnel how
to use the computer and programs.

In the application of the anti-
coagulation control problem, this
model appears to be adequate for rapid-
ly identifying patients who become
refractory to anticoagulation therapy,
estimating the time to reach the
therapeutic range, and determining the
proper dosage schedules to maintain
the desired prothrombin times. Fur-
thermore, this approach gives a
systematic method for dealing with
hard-to-control patients, and alerting
the physician early in the therapy
course that a particular patient may be
difficult to anticoagulate.

Acknowledgement

To William F. Powers for his
assistance in supplying the programs.

References

1. W.F. Powers, P.H. Abbrecht and
D.G. Covell, "Systems and Microcom-
puter Approach to Anticoagulation
Therapy," IEEE Trans Biomedical
Engineering, Vol. 27, pp. 520-523,
1980.

2. W.T. Sawyers and A.L. Finn,
"Digital Computer Assisted Warfarin:
Comparison of Two Models," Com-
puters and Biomedical Research, Vol.
12, pp. 221-231, 1979.

3. H. Wiegman and A. Vossepoel, A
Computer Program for Long Term
Anticoagulation Control, Vol. 5, p.
441, 1972.

4. W.F. Powers, Microcomputer
Approach to Anticoagulation Therapy,
University of Michigan, Ann Arbor,
Rep. AE 80-1, February 1980.

f0 -

tPROTHPOM
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•3 4-

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OSTER I OR I

l l f l i ( l 1 i

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£■' is' 29 ' iV 23
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Figon 2; Graphical display of the extend-
ed Kalman Filter values.

ft:Tfn t ■■ r~ ""* tor t, , ", r~' f~ !■"= ■*■ •»• t .-. «. .

tii itr. I ■' t o 1 K L L' '•.■'

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jjj a rci Copy

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ommerded Dcae

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load From Disl

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let Size Eciit

Figure 3: Example of the Menu selections
from the MAINTENANCE program.

Figure 4: Example of screen display for
recommended therapy from the mainte-
nance program.

MICRO - The 6502 Journal

No. 36 -May 1981

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No. 36 -May 1981

MICRO - The 6502 Journal

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MICRO - The 6502 Journal

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How Microsoft BASIC Works

What is a variable? How are
variables manipulated? This
article gives the answers to both
of these questions and
discusses the similarity of FNx
definitions to variables as well.

Greg Paris

625 Main St., #642

Roosevelt Island

New York, New York 10044

All computer languages are, to some
extent, symbolic in nature. This means
that addresses, constants and variables
may be used throughout a program and
be manipulated by their labels, instead
of using absolute or true values.
Although the use of symbols is often
merely convenient — as in assembler
texts — in many circumstances the
concept permits manipulations which
otherwise would be impossible.
Algebraic variables in BASIC or
FORTRAN are just one important case.
For these reasons, how a computer
language defines and manipulates sym-
bols is fundamental to the structure
and operation of whatever interfaces
between the user and the opcodes — an
interpreter, compiler, etc.

The varieties of symbol types allowed
in any language determine, to a great
extent, the power of that language to
solve certain programming problems.
The inherent accuracy of mathematical
calculations is another example where
the format of variable storage is
critical.

For these reasons, a logical first step
in dissecting the operation of the
BASIC interpreter is to find out how it
defines its symbols, and how it stores
them. The actual arithmetic and string
manipulation is more complicated, and
will be left for a later article.

This article is organized as follows.
First, I will make a few definitions.
This will level out most readers'

backgrounds, and obviously may be
skipped if you know the jargon. Next I
will describe the actual formats of both
numeric and string variables. Then I
will give a brief discussion of how
BASIC uses RAM. Finally, I will com-
bine all of the above to describe
variable storage formats, and explain
their coding.

Definitions

I caution the more advanced reader
that I am not a software development
engineer, and may not use the approved
industry-standard terminology.

Legal Variable Name: The BASIC
manual defines a legal variable name to
be "any alphabetic character, and [it]
may be followed by any alphanumeric
character... Any alphanumeric
characters after the first two are ig-
nored." In addition, one cannot embed
reserved words into the variable name
|A$ and AAAAAAA are legal variable
names; %A is not, and neither is
AGOTO).

Variable: To the interpreter, a
variable is anything that is not an array
(no joke!). Any time you need to refer
to only one number, or one string, or
one whatever, it will be called a
variable. For example, XI is a floating-
point (or FP) variable, XI % is an in-
teger variable, and Xl$ is a string
variable. They are stored in different
ways internally so the interpreter can-
not be confused by these three identical
variable symbols. You may be confused
however, so use caution in such cases.

Array: An array is any group of
variables which is referred to by a com-
mon legal variable name, followed by a
list of subscripts — also called indices.
The BASIC manual sometimes refers to
arrays as "matrices." An array may
contain either integer or FP numeric
data or strings, but no more than one
type per array. You are, in theory,

allowed 255 subscripts; the real restric-
tion is the line length which limits you
to twenty or so. For example, DIM
XI (2) allots space for a singly-
subscripted FP array, and has room for
3 numbers - X1(0), Xlfl), and Xl(2).
Further, DIM Xl%(20) allots space for
an array of 21 integer variables, and
DIM Xl$(10,3) partitions space for a
doubly-subscripted array of 44
[(10+l)x(3 + l)] different strings. (A
technical note: if an array is not dimen-
sioned before it is used, the interpreter
will automatically execute a DIM com-
mand and thus assign each subscript
the default value of 10.)

Header: I define a header as any in-
formation about a variable (how it is
stored or referred to) that is stored
along with the data to which it refers.
For example, if the interpreter requires
information about an array, including
its size, how many subscripts, and the
values of those subscripts, then the in-
terpreter will group all this informa-
tion, along with the variable name, in-
to a header — the small block of ' 'data' '
which immediately preceeds the real
data in the array. A header may be as
short and simple as the 2 bytes of an en-
coded variable name, or as detailed as
the example just given.

.WOR Address Format: When a
16-bit address is to be stored in an 8-bit
machine, it can be stored first byte
(MSB) first, second byte (LSB) second,
or in the reverse order. In assembler
notation, the MSB-first arrangement is
often referred to as ".DBY" (for "Dou-
ble BYte"), whereas the reversed order
— LSB-first — is called ".WOR" order
(for "WORd"). Almost all addresses
handled by the BASIC interpreter are
stored in .WOR format, including those
that may be embedded in headers.

Numeric Variables

There are two types of numeric data
allowed in BASIC: integer and floating-
point (FP) . An integer number is stored

No. 36 -May 1981

MICRO - The 6502 Journal

in two bytes, and can represent any in-
teger between +32,767 and -32,768.
An FP number is stored in 5 bytes (4
bytes on OSI) and can represent
numbers between ±1.7xl0 38 and
±2.94xl0- 3 ?, and zero. This format
for FP numbers allows at least 9
decimal digit accuracy at all times.

Since FP arithmetic as done by the
BASIC interpreter is not germane, I will
not detail its function in this article.
Suffice it to say that there exists, in
zero-page RAM, temporary storage
areas for two FP numbers. The one
most used is the floating-point ac-
cumulator (or FPAJ and is located at the
addresses shown in figure 1-A. The FPA
is five to seven bytes long — the second
byte of the FPA contains the sign of the
mantissa, which is incorporated into
the leftmost bit (MSB) of the mantissa
whenever a number is removed from
the FPA. (The use of this bit for the sign

need not confuse you, since in the FPA
this bit is defined as being set, unless
the number equals zero. Therefore, if it
will always be 1, then it can be ignored
during storage and used for another pur-
pose, namely, to store the sign of the
mantissa compactly.) In addition, there
is a byte (see figure 1-A) which actually
extends the FPA mantissa by 8 bits. It
is used internally in all arithmetic
operations, but is rounded off and strip-
ped whenever a variable is removed
from the FPA. The first byte of the FPA
is the exponent of the number plus $80.
If the number equals zero, then this
byte is zero.

Both types of variables, if referred to
before being assigned a specific
numeric value [i.e., if you use a
previously undefined variable), will be
filled with 0's — hence, the default
value in each case is zero.

String Variables

The "value" of a string variable,
and the information stored in a string
variable (or array) in RAM, are two dif-
ferent things. The two items actually
stored in the "variable" or "array" are
a pointer (or a list of pointers) in .WOR
format to the start of the string, and the
length of the string. The string may be
embedded in a program line, or stored
in "top free space" (high RAM).

If the string is empty ("null"), then
the byte for string length is set to zero,
and although it will then be ignored,
both bytes of the pointer are zeroed.
The size of any string is limited to 255
characters because a single byte is used
to indicate its length.

Figure 1-A: Locations of Floating-Point Accumulators

Computer:

AIM 65

Applesoft

OSI
(BASIC-
in-ROMJ

Old PET
(1.0)

New PET
(2.0, 4.0)

Length of FPA

6 bytes

7 bytes

5 bytes

6 bytes

Address of FPA

$00A9-$00AE

$009D-$00A3

$00AC-$00B0

$00B0-$00B5

$005E-$0063

FPA extension

$00B8

($00A3)

$00B2

$00B7

$0065

Figure 1B: BASIC Utility Pointers.

Computer:

AIM 65

Apple

OSI

(BASIC-in-ROMj

Old PET

New PET

Address of pointer to:

Start of

BASIC program

$0073

$0067

$0079

$007A

$0028

(address:)

($0212)

($0801)

($0301)

($0402)

Start of

variable storage

$0075

$0069

$007B

$007C

$002A

($PPPP)

Start of

array storage

$0077

$006B

$007D

$007E

$002C

($RRRR)

Start of

free space

$0079

$006D

$007F

$0080

$002E

($UNUN)

Top (end) of free space

$007B

$006F

$0081

$0082

$0030

($TTTT)

Top of memory

$007F

$004C

$0085

$0086

$0034

($NONO)

MICRO - The 6502 Journal

No. 36 -May 1981

Usei Functions

DEF and FNx are BASIC program
statements which allow a user to define
a unique function. Each FNx is labeled
by a legal variable name, and this is
why I discuss this statement in an arti-
cle on variables. As detailed later, the
BASIC interpreter stores a reference to
each function definition in a complex
header, filed under the variable name
which is assigned to it by the user.

How BASIC Uses RAM

A memory map of how BASIC parti-
tions space for its various needs is
shown in figure 1-B. "Top free space"
may be a new term to some readers.
When BASIC is commanded to operate
on strings, it designates an area in
unused memory as work space [from
$UNUN to $TTTT - 1), and then stores
the result of any operation in "top free
space" (from $TTTT to $NONO - 1).

Also listed in figure 1-B are the zero-
page locations which are reserved by
BASIC to store pointers to various ad-
dresses which are used frequently.
These pointers are initialized upon en-
try into BASIC, and are updated any
time the program is changed or run. All
pointers are stored in .WOR format.

How Variable Names are Encoded

BASIC reserves 2 bytes for the
variable name (symbol). However,
since the same name could refer either
to an integer, FP variable, or a string, it
must distinguish between them. It does
this by setting or clearing, in various
combinations, the otherwise unused
leftmost bit (MSB) of each of the two
bytes in the name. All four possible
permutations are used. The interpreter
performs this encoding during a RUN
whenever a new variable name is en-
countered, and uses the format describ-
ed in table 1. If a variable name is only
a single character, then the second
character space allotted to it is filled
with O's, except for the MSB, which is
set or cleared as needed.

Storage Formats

Most of the details of variable for-
mat and variable name encoding have
been described. All that remains is to
put the information together and
describe what is actually found in
memory from $PPPP to $UNUN- 1.

Table 1: Format of encoding different types of variable names.

If the legal variable name is AC, then:

if the variable is

then the symbol is encoded
as these two bytes:

a floating point numeric (no suffix)

$41, $43 (MSB each byte clear)

an integer numeric (suffix = %)

$C1, $C3 (MSB each byte set)

a string (suffix = $)

$41, $C3 (MSB first byte clear,
MSB second byte set)

an FNx definition variable

$C1, $43 (MSB first byte set,

MSB second byte clear)

Figure 2: Variable and Array Storage Formats

VARIABLES:

Floating Point Numeric

XX XX i. 2.3. 4. 5.

encoded ^

variable floating point number in

name storage format

Integer Numeric

XX XX 12 00 00 00

encoded
variable
name

allotted, but unused and
filled with zeros

String Header

XX XX ## PI PI 00 00

encoded
variable
name

FNx Header

number"

of bytes

in string

'•pointer, .WOR format
to first byte in string

XX XX P2P2P3P3QQ

encoded
variable
name

Jffirst byte of actual
definition for this FNx

pointer to first byte of FP number
used as dummy argument variable
(byte numbered 1 above)

pointer to the first byte of FNx
definition in BASIC program storage

No. 36 -May 1981

MICRO - The 6502 Journal

Variables are stored together, but
separate from the arrays. However, in-
teger numeric, FP numeric, string, and
FNx definition variables are all inter-
mixed. Arrays are stored in the next
higher allocated RAM, and are also in-
termixed. In both cases, the jumbled
order is actually a function of when
they are defined during the RUNning of
a program. Each variable or array that is
interpreted is assigned a space in the
order in which it is encountered, with
the variables and the arrays, each shut-
tled off to their respective spaces.

There is a reason for separating
variables from arrays. Each item stored
as a variable takes up exactly 7 bytes.
This makes searching for variables very
easy, as the interpreter's variable
pointer need only increment by 7 bytes
to look for the next variable. Since ar-
rays can vary greatly in size, this
technique is not applicable, and scan-
ning for individual array entries is
somewhat more time consuming.

Each time the program begins RUN-
ning, it executes a CLEAR instruction,
which erases any reference to any
variables and arrays which may have
previously been defined. This CLEAR
instruction sets the pointers located at
$0075, $0077, and $0079 (on the AIM|
to the same value — the address of the
last byte of program storage, plus one.
Similarly, the pointer at $007B ("top
free space") is set to equal the address
in $00 7F (top usable memory + 1).

The headers for variables and ar-
rays, and the formats in which they are
stored in RAM, are shown in figure 2.

The definition of a header should be
clearer now. In both types of numeric
variables, the header is simply the 2
bytes of the encoded variable name.
More complicated arrangements are
seen in the FNx header and the various
array headers.

Variables: For an FP variable, all 7
bytes are utilized. The last 5 bytes
represent the FP number, in RAM
storage form as described above.

Figure 2 continued

ARRAYS:

Floating Point Numeric

XX XX, M ##

encoded
variable
name

number of
subscripts
dimensioned

number of bytes in
array, including header
and all subsequent
bytes: .WOR format

five byte
floating point
number

XN XN is the maximum index
for each subscript (including
zero): .WOR format

Integer Numeric

XX XX

## ## ## XN XN XM XM

two byte integer number
(.DBY storage format)

1 2

header same as above;
variable name encoded
differently

String

XX XX

## ## ## XN XN XM XM ....

header same as above;
variable name encoded
differently

two byte pointer
to string: .WOR
format

MICRO - The 6502 Journal

No. 36 -May 1981

Legend for Figure 3

A. Test program in

BASIC.

B. Zero page pointers to

partitions in RAM (see figure 1-a).

C. Dump of tokenized test program (partial).

Note that D$ is

found at $025B, and the definition of FNQ at $0241.

D. Dump of variable and array storage.

Note that the order of

space assignment is identical to the discovered order

the program.

E. Contents of "top free

space", includes 'value' of E2$, found at $0FF1.

DIM AA(2) ,B%(2,3)

AA=2:B%=

DEF FNQ(X)=

X*AA

C=5.7207

D$ = "A STRING"

DIM C(2)

F%=-24

E2$="IS

NOT

"+D$

STOP

B.
<M> =

= 0073 12

BASIC PROGRAM STARTS AT $0212

< >

0075 98

VARIABLES START AT $0298

< >

0077 DO

ARRAYS START AT $02D0

< >

0079 ID

FREE SPACE STARTS AS $031D

< >

007B Fl

FREE SPACE ENDS AT $0FF1

< >

007F 00

TOP OF MEMORY IS $1000

C.
<M> =

=0212 26

NEXT LINE IS AT $0226

< >

0214 0A

THIS IS LINE 10

< >

0216 85

'DIM' TOKEN, SPACE

< >

0218 41

•AA"

< >

021A 28

1 (2'

< >

021C 29

'),'

< >

021E 42

■B%'

< >

0220 28

• (2 1

< >

0222 2C

',3'

< >

0224 29

' ) ' , END OF LINE

< >

0226 35

NEXT LINE IS AT $0235

< >

0228 14

THIS IS LINE 20

< >

022A 41

•AA'

< >

22C AC

'=* TOKEN, '2'

< >

022E 3A

' :B'

< >

0230 25

'%', '=' TOKEN

< >

0232 31

'17'

< >

0234 00

END OF LINE

< >

0235 46

NEXT LINE IS AT $0246

< >

0237 IE

THIS IS LINE 30

< >

0239 95

•DEF' TOKEN, SPACE

< >

023B 9F

•FN' TOKEN, 'Q'

< >

023D 28

' (X'

An integer variable only uses 4 of
the 7 bytes allotted to it. Use of integer
variables in your program therefore
wastes some space, but could save time
during interpretation.

The string "variable" has a 5-byte
header, made to fill 7 bytes by tacking a
bunch of zeros on the end.

The FNx header is very interesting.
It is filed as a variable because it is
defined with a variable name. Any legal
variable name may be used as its label.
In addition, any legal variable name
may be used as the dummy argument
variable, even one used elsewhere in
the program, because before the inter-
preter evaluates an FNx statement, it
saves the value which was originally
stored in the dummy variable on the
stack. If the dummy variable is a new
variable, it is automatically created,
allotted 7 bytes of space after the FNx
header, and appropriately labeled as an
FP variable. The FNx header is set up
whenever a DEF FNx is performed. If
this particular FNx is later redefined,
only the original header is changed.
The last byte in the header might not
be used by the interpreter; it seems to
be there only to clear the stack com-
pletely during the DEF FNx operation.

Arrays: Not only do arrays have
longer headers, but they also utilize
space more efficiently. There is no
minimum allotment of space, and con-
sequently, no filler bytes are necessary.
FNx arrays are not supported in this
version of BASIC.

The headers for each type of array
are essentially identical in format and
content. The first two bytes are the en-
coded array name (see table 1). The
next pair of bytes is a 16-bit number
(.WOR format), the total number of
bytes in the array. This includes the
header with all its subscripts spelled
out, and all the space allotted for the
variables or string pointers. The fifth
byte represents the number of sub-
scripts used. The remainder of the
header is a list of subscripts — a series
of 16-bit numbers in .WOR format, one
for each subscript — in an order that is
the REVERSE of the listed order in the
DIM statement.

No. 36 -May 1981

MICRO - The 6502 Journal

The actual storage format of the ar-
ray contents is much the same as for a
single variable. Each member of an FP
array is allotted five bytes for storage,
and each member of an integer array is
allotted two bytes. Therefore, in con-
trast to an integer variable, using in-
teger arrays not only saves interpreting
time but also a tremendous amount of
space as well. Each entry in a string ar-
ray is allotted three bytes, as before.

Within the array, individual
members are ordered in straightforward
fashion, but not as simply as you'd ex-
pect. Just as in the array header, the in-
dividual members of an array are in a
"reversed" ascending sequence. For
example, if the statement DIM A(2,4)
has been executed, then the order of
members in the array is A(0,0J, A(1,0),
A(2,0J, A|0,1|, A(l,l], A(2,l],...,
A(l,4), A(2,4). By analogy, this can be
extended to any number of subscripts.

An example is seen in figure 3. This
program is intended only to demon-
strate variable and array assignment.
Note that all the pointers — FNQ and
strings — point to the beginning of
their respective referents. All the
variables are ordered in the sequence in
which they were interpreted; the arrays
are similarly arranged in higher RAM.
Note the encoded variable names for
each assignment.

Summary

The following conclusions are of in-
terest to anyone wishing to save execu-
tion time and/or memory space. 1) The
use of an integer variable is generally a
waste, for two reasons: the integer
must be defined by a "%" each time it
occurs (at the cost of 1 byte per occur-
ence], and, since it takes up 5 bytes
anyway, even this doesn't save space.
2) An integer anay really does save
space, if it is of sufficient size. 3) You
can save a few bytes, and shorten ex-
ecution time slightly, by using as a
dummy argument variable one that has
already been used in the program. Its
actual value will not be lost during the
execution of an FNx.

These storage formats are not
specific to one machine, and apply to
those versions of Microsoft BASIC
which are used on AIM, SYM, PET,
OSI, Apple, etc.

023F

') ' , '=' TOKEN

0241

•X', '*' TOKEN

0243

'AA'

0245

END OF LINE

0246

NEXT LINE IS AT $0253

0248

THIS IS LINE 40

024A

■C 1 , '=' TOKEN

024C

•5. '

024E

'72'

0250

•07'

0252

END OF LINE

0253

NEXT LINE IS AT $0265

0255

THIS IS LINE 50

0257

'D$'

0259

'=' TOKEN, • "•

025B

•A '

025D

•ST 1

025F

•RI'

0261

'NG 1

0263

' " ' , END OF LINE

<M> =

=0298

029A

029C

029E

029F

02A1

02A3

02A5

02A6

02A8

02AA

02 AC

02AD

02AF

02B1

02B3

02B4

02B6

02B8

02BA

02BB

02BD

02BE

02C0

02C2

02C4

02C6

02C8

FP VARIABLE 'AA 1
VALUE IS 2

INTEGER VARIABLE 'B'
VALUE IS 17

FN 'C 1

DEFINED AT $0241

DUMMY VARIABLE VALUE AT $02AF

FP VARIABLE 'X'
VALUE IS

FP VARIABLE 'C
VALUE IS 5.7207

STRING VARIABLE 'D'
8 BYTES OF DATA
AT $025B

INTEGER VARIABLE 'F'
VALUE IS -24

(D$)

(F%)

MICRO -The 6502 Journal

No. 36 -May 1981

< >

02C9

STRING VARIABLE '2

' (E2$)

< >

02CB

15 BYTES OF DATA

< >

02CC

AT $0FF1

< >

02CE

< >

02D0

FP ARRAY 'AA 1

< >

02D2

USES 22 BYTES

< >

02D4

1 SUBSCRIPT

< >

02D5

SUBSCRIPT = 2

< >

02D7

ARRAY ELEMENTS ARE

ALL

< >

02E6

INTEGER ARRAY *B'

(B%)

< >

02E8

USES 33 BYTES

< >

02EA

2 SUBSCRIPTS

< >

02EB

SUBSCRIPT 2=3

< >

02ED

SUBSCRIPT 1=2

< >

02EF

ARRAY ELEMENTS ARE

ALL

<M> =

= 0FF1

'IS'

< >

0FF3

• n 1

< >

0FF5

'OT'

< >

0FF7

' A'

< >

0FF9

' S'

< >

OFFB

i TR i

< >

OFFD

•IN'

< >

OFFF

•G'

Ed. Note: Integer variables are not
supported by OSI and SYM BASIC.

All you need to know about
variables is here. Now you can design
an UNDIM command, or figure out
how to support FNx arrays. Or you can
construct your own DATA SAVE and
DATA LOAD routines for BASIC, link-
ing them to the USR function, if
necessary. What you will need in addi-
tion to this article is the knowledge of
which BASIC subroutines handle the
finding of specific variables, or of
specific entries in arrays, and how
these subroutines work. I plan to ad-
dress these and other topics in subse-
quent articles.

Greg Paris has been doing postdoctoral
research in neurobiology, and hopes to
program microcomputer-based
instrumentation for a living.

JMCftO

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No. 36 -May 1981

MICRO -The 6502 Journal

SYM-1
Communications Interface

This program acts as a traffic
cop in a three-way conversation
between a SYM, a human at a
CRT, and another computer via a
modem. It directs messages to
either the SYM or the modem on
the request of the human
operator, and makes sure the
human gets to see both ends of
the conversation.

Nicholas J. Vrtis
5863 Pinetree S.E.
Kentwood, Michigan 49508

It all started when 1 wanted to use an
accoustic coupler to transfer programs
to my SYM from another computer. At
first glance, it looks easy enough. Hook
the modem to the 20 mA TTY port, and
connect the CRT to the RS 232 port.
The problem with this arrangement is
that although the two devices are elec-
tronically separate, the SYM monitor
doesn't distinguish between data
received from these two ports. There
are status bits in TOUTFL ($A654)
which will allow me to control input
and output to each of the devices
separately, but the SYM still won't tell
me where a character came from. There
is also a bit in TECHO ($A653J which
can be used to control echoing
characters to either the CRT or TTY.
The real problem though, is that I only
wanted some data from the modem to
be handed to the SYM monitor. It
wouldn't have the foggiest idea what to
do with a sign-on request from the
other computer. The same is true for
data from the CRT, only worse. Some
of that had to go to the monitor to tell it
to expect a program, and some had to
go to the modem to tell the other com-
puter to start sending it. Finally, I
wanted to see all the data from both the
monitor and modem on the CRT, and
didn't want the monitor data to be
transmitted by the modem. For the
same reason I couldn't give data from
the modem to the monitor.

The solution turned out to be
shorter than I first expected. About half
of the work involved setting up the
hardware and control bits the right
way, and the other half was writing a
short interface routine. Mechanically,
the modem and the CRT have to be set
up in full duplex mode, so they don't
echo any characters. The SYM monitor
will take care of that if we set the high
order bit of TECHO on. The echo por-
tion of the SYM monitor terminal in-
put routine doesn't care where a bit
comes from when it echoes it. Bits four
and five of TOUTFL control which
device the input byte is echoed to. It
doesn't necessarily have to be the one it
came from. If we set TOUTFL to enable
input from both the CRT and the TTY,
but only output to the CRT, then
anything from either input device will
be echoed to the CRT. Setting TOUTFL
this way also means that any output
from the monitor will only go to the
CRT port, and not to the modem. It
also means that anything entered at the
CRT will not get transmitted to the
modem, so we will have to use soft-
ware later on to turn the TTY output
bit back on when we want it. Finally,
this requires that the modem and the
CRT are both operating at the same
baud rate.

Now that we have the system all
wired up, and the bits set, we find that
things are arranged so anybody can talk
to the CRT, but nobody can talk to
anybody else accidentally. Now for a
little software to add some smarts to
the thing, and we are all set. The SYM
vectors all input via an address in
System RAM at $A661, called INVEC.
By putting the address of our routine
there, it will have a chance to look at
all the input and decide what to do with
it, to a certain extent. We won't bother
with the output side; we just have to be
careful not to go to the monitor with
the TTY output enable bit on.

There are three characters which
have special meaning to these input
routines. The BELL character (hex $07
— control G on my CRT) is used to in-
dicate the start of a string to go to the
monitor. The BELL is not sent to the
monitor, but all characters following it,
up to and including the next carriage
return (hex $0D), do get sent. The
semicolon (hex $3BJ is very similar in
meaning to the BELL, except that the
semicolon itself is also returned to the
monitor. This allows the transfer of
paper-tape-format hex dumps to the
SYM without requiring my program to
precede each line with a BELL (and
driving me crazy) . I left four extra bytes
in the program after the compare for
the semicolon so you could change it to
look for a range of characters. If you $T\
patch the following in, you can check \y
for numerics as the key character in-
stead of the semicolon.

CMP #'0' Check if less than
ASCII zero

BCC TRYP Branch if less

CMP #':' Colon is ASCII nine
+ 1

BCS TRYP Branch if greater
or equal

This arrangement would be useful
when transferring a BASIC program or
other data with line numbers. Watch
out for the number of null characters
which BASIC needs at the end of a line
for timing. The final special input
character is the DLE [hex $10 — con-
trol P on my CRT) . This performs the
modem function corresponding to the
BELL for the monitor. The method is
different, though. Instead of returning a
character via an RTS, the DLE routine
causes the TTY output enable bit to be
turned on in TOUTFL. When this bit is
on, the SYM input routines will echo
all characters from the CRT to both the
CRT and the modem on the TTY port. g^
As with the BELL, the 'to modem' \J'
mode is in effect up to and including

MICRO - The 6502 Journal

No. 36 -May 1981

the next carriage return. Unfortunate-
ly, there isn't any way to implement a
modem equivalent of the semicolon.
Once a character has been received
from the CRT, there just isn't enough
time to turn around and transmit it via
the TTY port. It technically could be
done, but the person at the CRT would
have to make sure that he waited at
least one character time between each
keystroke. If you type too fast, you end
up transmitting garbage.

The special input characters are
looked for only when the output hasn't
already been directed to either the
monitor or the modem. Similarly, the
carriage return is only meaningful if
one of the output modes is set. Be
careful, though, because a carriage
return from either the modem or the
CRT will reset the flags to output to
neither the monitor nor the modem.
The special input characters don't have
to be at the beginning of a line, so it is
possible to have the 'to monitor mode'
set accidentally by the other computer.
If you know, and/or think that these
characters might arrive unexpectedly
from the other computer, you may
want to change the character looked for
in the comparisons to something you
probably won't be getting. The routines
are not set up to allow a 'to modem'
and 'to monitor' mode at the same
time. You can have one, or the other, or
neither, but not both. If you want a pro-
gram on the SYM to talk to the modem,
simply have it turn on the TTY output
bit in TOUTFL before outputting, and
turn it off when done.

My final disclaimer is that these
routines were not designed for long in-
volved conversations between you and
other computers. They were designed
merely to transfer programs to the
SYM. It can get rather tedious (not to
mention noisy) preceding everything
with BELL'S and DLE.

SYM-1 Modem Communications
Interfacer

Theory:

1. The terminal is connected to the
CRT RS-232 port, the modem is
connected to the TTY port.

2. TOUTFL is set to $D0 — TTY and
CRT input enabled, and TTY output
disabled. Therefore any input from
either TTY or CRT will appear on
the CRT.

0800

j ******************************

0800

;» SYM

-1 MODEM COMMUNICATIONS *

0800

INTERFACE ROUTINE

0800

;* BY NICHOLAS J. VRTIS

0800

. ******************************

0800

MODFLG

EPZ $FA

(SPARE SYM-1 P.Z. AREA

0800

TOUTFL EQU $A654

/TERMINAL OUTPUT FLAG BYTE

0800

INTCHR EQU $8A58

.-TERMINAL INPUT ROUTINE

0800

ACCESS EQU $8B86

0800

OFC0

ORG $FC0

;BACK OUT OF THE WAY

0FC0

OBJ $800

0FC0

0FC0 20588A

MODEM

JSR INTCHR

;GET AN INPUT CHARACTER

0FC3 297F

AND l$7F

; STRIP PARITY

0PC5 24FA

BIT MODFLG

.■CHECK CURRENT MODE

0FC7 3027

BMI TOMON

.-BRANCH IF TO THE MONITOR

0PC9 702C

BVS TOMOEM

,-OR IF TO THE MODEM

0PCB

0FCB C93B

CMP 1';'

;IS THIS FOR THE MONITOR

0FCD D007

BNE TRYP

;NO

0PCF

0PCF EAEAEA

HEX EAEAEAEA

,- PATCH AREA FOR EXTRA COMPARE

0FD2 EA

0FD3

0FD3 66FA

ROR MODFLG

jROLL CARRY INTO FLAG FOR "TO MONITOR'

0FD5 60

RTS

,-AND THIS WILL GIVE IT TO MONITOR

on*

0FD6 C907

TRYP

CMP IS07

.■MONITOR SELECT CODE ??

OH* D004

BNE TRYS

;NO

0FDA 66FA

ROR MODFLG

;ROLL CARRY TO SET "TO MONITOR' BIT

0FDC D0E2

BNE MODEM

,-AND IOIORE THIS CHARACTER

0FDE

OFDE C910

TRYS

CMP #$10

;MODEM SELECT CODE?

0FE0 CODE

BNE MODEM '

,-NO— IGNORE THIS CHARACTER

0FE2

0FE2 A2F0 •

LDX l$F0

.-TURN ON TTY OUTPUT ALSO

0FE4 A940

LDA l$40

;YES— TURN ON 'TO MODEM' MODE

0FE6 20868B

STFLAG JSR ACCESS

.-MAKE SURE CAN UPDATE SYSTEM RAM

0FE9 8E54A6

STX TOUTFL

.-STORE NEW FLAG SETTING

0PBC 85FA

STA MODFLG

; STORE NEW MODE SETTING

0FEE DODO

BNE MODEM

; UNCONDITIONAL— IGNORE THIS ONE

0FF0

.*
i

0FF0 C90D

TOMON

CMP i$0D

;IS THIS NEXT CARRIAGE RETURN?

0FF2 D002

BNE *+4

;NO— PASS IT ON

0FF4 85FA

STA MODFLG

,- YES— SET MODE BITS OFF

0FF6 60

RTS

,-AND RETURN TO THE MONITOR

0FF7

.*
i

0FF7 C90D

TOMODM CUP #$0D

,-WAS IT A CARRIAGE RETURN?

0FF9 D0C5

BNE MODEM

;NO-IT IS ALREADY ECHOED TO THE TTY

OFFB A2D0

LDX #$DO

jYES— TURN OFF TTY ECHO BIT

0FFD D0E7

BNE STFLAG

,-NEK FLAG, $0D TURNS OFF MODE SET

0FFF

ZZZEND EQU *-l

.-LAST BYTE OF PROGRAM

3. TECHO must be set to $80 so input
is echoed to the CRT.

4. THE CRT must be in full duplex
mode.

5. Address of 'MODEM' replaces
address of 'INTCHR' in 'INVEC.

6. 'MODEM' is normally waiting to
return a character to the monitor via
the RTS.

7. The CRT and TTY must be at the
same speed.

8. To direct output to the modem from
the CRT, the TTY echo bit is turned
on in TOUTFL.

9. No direct provision is made for the
CPU to talk to the modem.

Functions:

';' gets returned to the monitor and
sets 'TO MONITOR' mode.

All following characters to next
C/R also go to monitor.

Bell ($07) does not go to monitor,
but does set 'TO MONITOR' mode. All
following characters to next C/R also
go to the monitor.

DLE ($10) does not go to modem,
but does set 'TO MODEM' mode. All
following characters to next C/R also
go to the modem.

JUCRO

No. 36 -May 1981

MICRO -The 6502 Journal

Annual Index

June1980— May 1981
(Issues 25 - 36)

Articles

Title/Author

AIM

Share Your AIM Programs

Jody Nells
AIM-65 File Operations

Christopher J. Flynn
Satellite Tracking with the AIM-65

C.R. MacCluer
Loading KIM-1 Tapes to AIM

Larry P. Gonzalez
Compact

Steve Bresson
Tiny PILOT for the AIM

Larry Kollar and Carl Qutekunst
An improved Morse Code Receive Routine and Interface

Marvin L DeJong
Biorhythm: An AIM BASIC Programming Exercise

P.E. Butcher
AIM 65 File Operations: Writing Text Files with BASIC

Christopher J. Flynn
A Random-Character Morse Code Teacher for the Al M 65

Eugene V. Weiner, Marvin L. DeJong, Russell V. Lenth
AIM 65 File Operations

Christopher J. Flynn
One-Dimensional Life on the AIM 65

Larry Kollar
A Relocating Loader for AIM Tape

Mel Evans
MEMSEARCHfortheAIM65

Boo Kovacs

APPLE

A Little Plus For Your Apple II

Craig Peterson
APPLE II Integer BASIC Program List by Page

Dave Partyka
BASIC and Machine Language Transfers with
Micromodem II

George Dombrowski
TRACER: A Debugging Tool for the APPLE II

ft Kovacs
Zoom and Squeeze

Gary B. Little
Data Statements Revisited

Virginia Lee Brady
Better Utilization of Apple Computer Renumber and
Merge Program

Frank 5. Chipchase
Solar System Simulation with or without an Apple II

David A. Partyka
Applesoft Floating Point Routines

R.M. Mottola
Business Dollars and Sense In Applesoft

Barton M. Bauers, Jr.
Creating Shape Tables, Improved!

Pefer A. Cook
A Versatile Hi-Res Function Plotter for the Apple II

David P. Allen
Mean 14: A Pseudo-Machine Floating Point Processor for
the Apple II

R.M. Mottola
PRINT USING for Applesoft

Gary A. Morris
Paged Printer Output for the APPLE

Gary Little
Cassette Label Program

Dawn E. Ellis
Step and Trace for the APPLE II Plus

Craig Peterson
Graphing Rational Functions

Ron Carlson
An Apple Flavored Lifesaver

Gregory L Tibbetts
Creating an Applesoft BASIC Subroutine Library

N.R. McBurney

Issue/Page